title: Null check operator used on a null value - BloC with Null-Saftey
body: <p>I tried to understand why <code>topRated</code> and <code>popular</code> always get null value although results print it's value in console
  I'm using <strong>The Movie DB Api</strong></p>
  <pre><code>import 'package:expandable/expandable.dart';
  import 'package:flutter/material.dart';
  import 'package:flutter_bloc/flutter_bloc.dart';
  import 'package:g_movies/models/movies_model.dart';
  import 'package:g_movies/shared/cubit/cubit.dart';
  import 'package:g_movies/shared/cubit/states.dart';
  import 'package:g_movies/shared/styles/colors.dart';
  import 'package:google_fonts/google_fonts.dart';
  
  class MoviesLayout extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return BlocProvider(
        create: (BuildContext context) {
          return MoviesCubit()
            ..getTopRatedData()
            ..getPopularData();
        },
        child: BlocConsumer&lt;MoviesCubit, MoviesStates&gt;(
          listener: (context, state) {},
          builder: (context, state) {
            return Scaffold(
              appBar: AppBar(
                title: Text(
                  'GMovies',
                  style: GoogleFonts.oswald(
                    fontWeight: FontWeight.bold,
                    fontSize: 24,
                    color: defaultColor,
                  ),
                ),
                actions: [
                  Padding(
                    padding: const EdgeInsets.symmetric(horizontal: 20),
                    child: CircleAvatar(
                      radius: 20,
                      child: IconButton(
                        icon: Icon(Icons.person),
                        onPressed: () {},
                      ),
                    ),
                  ),
                ],
              ),
              body: SingleChildScrollView(
                child: Padding(
                  padding: const EdgeInsets.all(20.0),
                  child: Column(
                    children: [
                      ExpandablePanel(
                        theme: ExpandableThemeData(
                          headerAlignment: ExpandablePanelHeaderAlignment.center,
                        ),
                        header: Row(
                          children: [
                            Text(
                              'Top Rated',
                              style: TextStyle(
                                fontWeight: FontWeight.bold,
                                fontSize: 22,
                              ),
                            ),
                            SizedBox(
                              width: 5,
                            ),
                            Text(
                              'Movies',
                              style: TextStyle(
                                fontSize: 22,
                              ),
                            ),
                          ],
                        ),
                        collapsed: SizedBox(
                          height: 2,
                        ),
                        expanded: SizedBox(
                          width: double.infinity,
                          height: 200,
                          child: ListView.separated(
                            shrinkWrap: true,
                            scrollDirection: Axis.horizontal,
                            itemBuilder: (context, index) =&gt; movieItem(
                                MoviesCubit.get(context)
                                    .topRated!
                                    .results[index]),
                            separatorBuilder: (context, index) =&gt; SizedBox(
                              width: 10,
                            ),
                            itemCount:
                                MoviesCubit.get(context).topRated!.results.length,
                          ),
                        ),
                      ),
                      SizedBox(
                        height: 10,
                      ),
                      ExpandablePanel(
                        theme: ExpandableThemeData(
                          headerAlignment: ExpandablePanelHeaderAlignment.center,
                        ),
                        header: Row(
                          children: [
                            Text(
                              'Popular',
                              style: TextStyle(
                                fontWeight: FontWeight.bold,
                                fontSize: 22,
                              ),
                            ),
                            SizedBox(
                              width: 5,
                            ),
                            Text(
                              'Movies',
                              style: TextStyle(
                                fontSize: 22,
                              ),
                            ),
                          ],
                        ),
                        collapsed: SizedBox(
                          height: 2,
                        ),
                        expanded: SizedBox(
                          width: double.infinity,
                          height: 200,
                          child: ListView.separated(
                            shrinkWrap: true,
                            scrollDirection: Axis.horizontal,
                            itemBuilder: (context, index) =&gt; movieItem(
                                MoviesCubit.get(context).popular!.results[index]),
                            separatorBuilder: (context, index) =&gt; SizedBox(
                              width: 10,
                            ),
                            itemCount:
                                MoviesCubit.get(context).popular!.results.length,
                          ),
                        ),
                      ),
                      SizedBox(
                        height: 10,
                      ),
                      ExpandablePanel(
                        theme: ExpandableThemeData(
                          headerAlignment: ExpandablePanelHeaderAlignment.center,
                        ),
                        header: Row(
                          children: [
                            Text(
                              'Coming',
                              style: TextStyle(
                                fontWeight: FontWeight.bold,
                                fontSize: 22,
                              ),
                            ),
                            SizedBox(
                              width: 5,
                            ),
                            Text(
                              'Soon',
                              style: TextStyle(
                                fontSize: 22,
                              ),
                            ),
                          ],
                        ),
                        collapsed: SizedBox(
                          height: 2,
                        ),
                        expanded: SizedBox(
                          width: double.infinity,
                          height: 200,
                          child: ListView.separated(
                            shrinkWrap: true,
                            scrollDirection: Axis.horizontal,
                            itemBuilder: (context, index) =&gt; movieItem(
                                MoviesCubit.get(context)
                                    .topRated!
                                    .results[index]),
                            separatorBuilder: (context, index) =&gt; SizedBox(
                              width: 10,
                            ),
                            itemCount: 10,
                          ),
                        ),
                      ),
                      SizedBox(
                        height: 10,
                      ),
                      ExpandablePanel(
                        theme: ExpandableThemeData(
                          headerAlignment: ExpandablePanelHeaderAlignment.center,
                        ),
                        header: Row(
                          children: [
                            Text(
                              'Now',
                              style: TextStyle(
                                fontWeight: FontWeight.bold,
                                fontSize: 22,
                              ),
                            ),
                            SizedBox(
                              width: 5,
                            ),
                            Text(
                              'Playing',
                              style: TextStyle(
                                fontSize: 22,
                              ),
                            ),
                          ],
                        ),
                        collapsed: SizedBox(
                          height: 2,
                        ),
                        expanded: SizedBox(
                          width: double.infinity,
                          height: 200,
                          child: ListView.separated(
                            shrinkWrap: true,
                            scrollDirection: Axis.horizontal,
                            itemBuilder: (context, index) =&gt; movieItem(
                                MoviesCubit.get(context)
                                    .topRated!
                                    .results[index]),
                            separatorBuilder: (context, index) =&gt; SizedBox(
                              width: 10,
                            ),
                            itemCount: 10,
                          ),
                        ),
                      ),
                    ],
                  ),
                ),
              ),
            );
          },
        ),
      );
    }
  
    Widget movieItem(Result model) {
      return ClipRRect(
        borderRadius: BorderRadius.circular(20),
        child: Image(
          fit: BoxFit.fill,
          width: 140,
          height: 210,
          image:
              NetworkImage('http://image.tmdb.org/t/p/w500${model.posterPath}'),
        ),
      );
    }
  }
  </code></pre>
  <p>and my Cubit :</p>
  <pre><code>import 'package:flutter_bloc/flutter_bloc.dart';
  import 'package:g_movies/models/movies_model.dart';
  import 'package:g_movies/shared/cubit/states.dart';
  import 'package:g_movies/shared/network/end_points.dart';
  import 'package:g_movies/shared/network/remote/dio_helper.dart';
  
  class MoviesCubit extends Cubit&lt;MoviesStates&gt; {
    MoviesCubit() : super(InitialState());
  
    static MoviesCubit get(context) =&gt; BlocProvider.of(context);
  
    MoviesModel? topRated;
  
    void getTopRatedData() {
      emit(GetTopRatedLoadingState());
      DioHelper.getData(
        url: topRatedMovies,
      ).then((value) {
        topRated = MoviesModel.fromJson(value.data);
        //print(value.data.toString());
        print(topRated!.results);
        emit(GetTopRatedSuccessState());
      }).catchError((error) {
        print(error);
        emit(GetTopRatedErrorState(error.toString()));
      });
    }
  
    MoviesModel? popular;
  
    void getPopularData() async {
      emit(GetPopularLoadingState());
      DioHelper.getData(
        url: popularMovies,
      ).then((value) {
        popular = MoviesModel.fromJson(value.data);
        //print(value.data.toString());
        print(popular!.results);
        emit(GetPopularSuccessState());
      }).catchError((error) {
        print(error);
        emit(GetPopularErrorState(error.toString()));
      });
    }
  }
  </code></pre>
  <p>Console :</p>
  <pre><code>Performing hot restart...
  Syncing files to device AOSP on IA Emulator...
  Restarted application in 3,156ms.
  I/flutter (12795): onCreate -- MoviesCubit
  I/flutter (12795): onChange -- MoviesCubit, Change { currentState: Instance of 'InitialState', nextState: Instance of 'GetTopRatedLoadingState' }
  I/flutter (12795): onChange -- MoviesCubit, Change { currentState: Instance of 'GetTopRatedLoadingState', nextState: Instance of 'GetPopularLoadingState' }
  
  ======== Exception caught by widgets library =======================================================
  The following _CastError was thrown building BlocBuilder&lt;MoviesCubit, MoviesStates&gt;(dirty, state: _BlocBuilderBaseState&lt;MoviesCubit, MoviesStates&gt;#faf5b):
  Null check operator used on a null value
  
  The relevant error-causing widget was: 
    BlocBuilder&lt;MoviesCubit, MoviesStates&gt; file:///C:/src/flutter/.pub-cache/hosted/pub.dartlang.org/flutter_bloc-7.0.1/lib/src/bloc_consumer.dart:131:12
  When the exception was thrown, this was the stack: 
  #0      MoviesLayout.build.&lt;anonymous closure&gt; (package:g_movies/layout/movies_layout.dart:91:64)
  #1      BlocBuilder.build (package:flutter_bloc/src/bloc_builder.dart:91:57)
  #2      _BlocBuilderBaseState.build (package:flutter_bloc/src/bloc_builder.dart:163:21)
  #3      StatefulElement.build (package:flutter/src/widgets/framework.dart:4691:27)
  #4      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4574:15)
  ...
  ====================================================================================================
  
  ======== Exception caught by widgets library =======================================================
  The following _CastError was thrown building BlocBuilder&lt;MoviesCubit, MoviesStates&gt;(dirty, state: _BlocBuilderBaseState&lt;MoviesCubit, MoviesStates&gt;#faf5b):
  Null check operator used on a null value
  
  The relevant error-causing widget was: 
    BlocConsumer&lt;MoviesCubit, MoviesStates&gt; file:///C:/Users/agala/.AndroidStudio4.0/g_movies/lib/layout/movies_layout.dart:19:14
  When the exception was thrown, this was the stack: 
  #0      MoviesLayout.build.&lt;anonymous closure&gt; (package:g_movies/layout/movies_layout.dart:91:64)
  #1      BlocBuilder.build (package:flutter_bloc/src/bloc_builder.dart:91:57)
  #2      _BlocBuilderBaseState.build (package:flutter_bloc/src/bloc_builder.dart:163:21)
  #3      StatefulElement.build (package:flutter/src/widgets/framework.dart:4691:27)
  #4      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:4574:15)
  ...
  ====================================================================================================
  I/flutter (12795): Invalid argument(s) (input): Must not be null
  I/flutter (12795): onChange -- MoviesCubit, Change { currentState: Instance of 'GetPopularLoadingState', nextState: Instance of 'GetPopularErrorState' }
  I/flutter (12795): [Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result', Instance of 'Result']
  I/flutter (12795): onChange -- MoviesCubit, Change { currentState: Instance of 'GetPopularErrorState', nextState: Instance of 'GetTopRatedSuccessState' }
  </code></pre>