title: unexpected null value Flutter
body: <p>hey guys i m new in dart and flutter
  when i run the project i face an error that <a href="https://i.stack.imgur.com/zW120.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/zW120.png" alt="enter image description here" /></a>says unexpected null value i couldn't find where is the mistake, i think the problem is in Null Safety.
  I have three classes two of them are for screen and one is a modle,</p>
  <pre><code>    import 'package:enpc_site/screens/body_page.dart';
  import 'package:enpc_site/screens/navigate_bar.dart';
  import 'package:enpc_site/screens/our_services.dart';
  import 'package:flutter/material.dart';
  
  class Home extends StatefulWidget {
    @override
    _HomeState createState() =&gt; _HomeState();
  }
  
  class _HomeState extends State&lt;Home&gt; {
    @override
    Widget build(BuildContext context) {
      return Scaffold(
        appBar: PreferredSize(
          preferredSize: Size.fromHeight(150),
          child: AppBar(
            backgroundColor: Colors.black,
            flexibleSpace: NavigateBar(),
          ),
        ),
        body: Container(
          decoration: BoxDecoration(
              gradient: LinearGradient(
                  begin: Alignment.topCenter,
                  end: Alignment.bottomCenter,
                  colors: [
                Color.fromARGB(255, 0, 0, 0),
                Color.fromARGB(255, 49, 8, 8)
              ])),
          height: double.infinity,
          child: Padding(
              padding: EdgeInsets.symmetric(vertical: 20, horizontal: 100),
              child: SingleChildScrollView(
                child: Column(
                  children: [
                    Padding(
                      padding: const EdgeInsets.only(top: 200),
                      child: WhoWe(),
                    ),
                    Padding(
                      padding: const EdgeInsets.only(top: 200),
                      child: OurServices(), // here i'm calling my second screen class
                    )
                  ],
                ),
              )),
        ),
      );
    }
  }
  </code></pre>
  <p>the second class</p>
  <pre><code>import 'package:enpc_site/models/products.dart';
  import 'package:flutter/material.dart';
  class OurServices extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
      return LayoutBuilder(
        builder: (context, constraint) {
          return BodyPage();
        },
      );
    }
  }
  
  class BodyPage extends StatelessWidget {
    @override
    Widget build(BuildContext context) {
       Products? product;
       String image = product!.products[0].image;
       String name = product.products[0].name;
       String desc = product.products[0].discription;
      return Container(
        width: double.infinity,
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: [
            Text(
              &quot;SERVICES&quot;,
              style: TextStyle(fontSize: 25, color: Colors.white),
            ),
            SizedBox(
              height: 20,
            ),
            Text(
              &quot;CE QUE NOUS PRODUISON&quot;,
              style: TextStyle(
                  fontSize: 40, fontWeight: FontWeight.bold, color: Colors.white),
            ),
            SizedBox(
              height: 40,
            ),
            SingleChildScrollView(
              scrollDirection: Axis.horizontal,
                child: Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  Container(
                    height: 500,
                    width: 500,
                    decoration: BoxDecoration(
                      color: Color.fromARGB(100, 240, 240, 240),
                      borderRadius: BorderRadius.circular(10)
                    ),
                    child: Padding(
                      padding: const EdgeInsets.all(40),
                      
                      child: Column(
                        mainAxisAlignment: MainAxisAlignment.spaceBetween,
                        crossAxisAlignment: CrossAxisAlignment.center,
                        children: [
                          Image.asset('$image' , width: 400, height: 300,),
                          Text(
                            '$name',
                            style: TextStyle(color: Colors.white, fontSize: 20, fontWeight: FontWeight.bold),
                          ),
                          RichText(
                              text: TextSpan(text: '$desc',
                              style: TextStyle(color: Colors.white, fontSize: 15), ),
                              
                            ),
                        ],
                      ),
                    ),
                  ),
                  SizedBox(
                    width: 20,
                  ),
                  Container(
                    height: 500,
                    width: 500,
                    decoration: BoxDecoration(
                      color: Color.fromARGB(100, 240, 240, 240),
                      borderRadius: BorderRadius.circular(10)
                    ),
                    child: Padding(
                      padding: const EdgeInsets.all(40),
                      
                      child: Column(
                        mainAxisAlignment: MainAxisAlignment.spaceBetween,
                        crossAxisAlignment: CrossAxisAlignment.center,
                        children: [
                          Image.asset('assets/images/port.png', width: 400, height: 300,),
                          Text(
                            'Gaine Plastic',
                            style: TextStyle(color: Colors.white, fontSize: 20, fontWeight: FontWeight.bold),
                          ),
                          RichText(
                              text: TextSpan(text: 'Les gaines ou fourreaux de protection utilisables dans l\'habitat dépendent de la norme NF C 15-100 relative aux installations électriques à basse tension',
                              style: TextStyle(color: Colors.white, fontSize: 15), ),
                              
                            ),
                        ],
                      ),
                    ),
                  ),
                  SizedBox(
                    width: 20,
                  ),
                  Container(
                    height: 500,
                    width: 500,
                    decoration: BoxDecoration(
                      color: Color.fromARGB(100, 240, 240, 240),
                      borderRadius: BorderRadius.circular(10)
                    ),
                    child: Padding(
                      padding: const EdgeInsets.all(40),
                      
                      child: Column(
                        mainAxisAlignment: MainAxisAlignment.spaceBetween,
                        crossAxisAlignment: CrossAxisAlignment.center,
                        children: [
                          Image.asset('assets/images/Sheet.png', width: 400, height: 300,),
                          Text(
                            'Gaine Plastic',
                            style: TextStyle(color: Colors.white, fontSize: 20, fontWeight: FontWeight.bold),
                          ),
                          RichText(
                              text: TextSpan(text: 'Les gaines ou fourreaux de protection utilisables dans l\'habitat dépendent de la norme NF C 15-100 relative aux installations électriques à basse tension',
                              style: TextStyle(color: Colors.white, fontSize: 15), ),
                              
                            ),
                        ],
                      ),
                    ),
                  ),
                  SizedBox(width: 20,),
                  Container(
                    height: 500,
                    width: 500,
                    decoration: BoxDecoration(
                      color: Color.fromARGB(100, 240, 240, 240),
                      borderRadius: BorderRadius.circular(10)
                    ),
                    child: Padding(
                      padding: const EdgeInsets.all(40),
                      
                      child: Column(
                        mainAxisAlignment: MainAxisAlignment.spaceBetween,
                        crossAxisAlignment: CrossAxisAlignment.center,
                        children: [
                          Image.asset('assets/images/gainePlastic.png', width: 400, height: 300,),
                          Text(
                            'Gaine Plastic',
                            style: TextStyle(color: Colors.white, fontSize: 20, fontWeight: FontWeight.bold),
                          ),
                          RichText(
                              text: TextSpan(text: 'Les gaines ou fourreaux de protection utilisables dans l\'habitat dépendent de la norme NF C 15-100 relative aux installations électriques à basse tension',
                              style: TextStyle(color: Colors.white, fontSize: 15), ),
                              
                            ),
                        ],
                      ),
                    ),
                  ),
                ],
              ),
            )
          ],
        ),
      );
    }
  }
  </code></pre>
  <p>and this is the model class Product</p>
  <pre><code>    class Products {
      final String name, discription;
      final String image;
    
  
  
    Products(
        { required this.name, required this.discription, required this.image});
  List&lt;Products&gt; products = [
      Products(
          name: 'Gaine Plastic',
          discription:
              'Les gaines ou fourreaux de protection utilisables dans l\'habitat dépendent de la norme NF C 15-100 relative aux installations électriques à basse tension ',
          image: 'assets/images/gainePlastic.png'),
      Products(
          name: 'Gaine Plastic',
          discription:
              'Les gaines ou fourreaux de protection utilisables dans l\'habitat dépendent de la norme NF C 15-100 relative aux installations électriques à basse tension ',
          image: 'assets/images/port.png'),
      Products(
          name: 'Gaine Plastic',
          discription:
              'Les gaines ou fourreaux de protection utilisables dans l\'habitat dépendent de la norme NF C 15-100 relative aux installations électriques à basse tension ',
          image: 'assets/images/Sheet.png'),
      Products(
          name: 'Gaine Plastic',
          discription:
              'Les gaines ou fourreaux de protection utilisables dans l\'habitat dépendent de la norme NF C 15-100 relative aux installations électriques à basse tension ',
          image: 'assets/images/gainePlastic.png'),
      Products(
          name: 'Gaine Plastic',
          discription:
              'Les gaines ou fourreaux de protection utilisables dans l\'habitat dépendent de la norme NF C 15-100 relative aux installations électriques à basse tension ',
          image: 'assets/images/gainePlastic.png'),
    ];
    
  }
  </code></pre>