title: Cannot read property 'Symbol(dartx._get)' of null
body: <p>I'm trying to call API in the web app is show this error and Android and iOS Working fine. I don't understand why happening.I'm using retrofit and dio to call api's.</p>
  <pre><code>   import 'dart:convert';
      import 'package:flutter/cupertino.dart';
      import 'package:web_app/utils/constants.dart';
      
      class ServiceError {
        static BuildContext context;
      
        ServiceError(BuildContext context) {
          context = context;
        }
      
        void getError(final res) {
  print(&quot;MyError&quot; + res.toString()); // I got null value and this working fine in android and iOS. only i get problem in web app
          final jsonResponse = jsonDecode(res.toString());
          ApiError apiError = ApiError.fromJson(jsonResponse);
          print(&quot;MyError&quot; + apiError.status);
          print(&quot;MyCode&quot; + apiError.message);
      
          if (apiError.responseCode == 500) {
            Constants.toast(apiError.message);
          } else {
            Constants.toast(apiError.message);
          }
        }
      }
  </code></pre>
  <p>I got this error</p>
  <pre><code>TypeError: Cannot read property 'Symbol(dartx._get)' of null
      at new service_errors.ApiError.fromJson (http://localhost:44059/packages/web_app/service_errors/service_errors.dart.lib.js:103:36)
      at service_errors.ServiceError.new.getError (http://localhost:44059/packages/web_app/service_errors/service_errors.dart.lib.js:23:22)
      at http://localhost:44059/packages/web_app/forgot_password/reset_password.dart.lib.js:6485:58
      at _RootZone.runUnary (http://localhost:44059/dart_sdk.js:37533:58)
      at _FutureListener.catchError.handleError (http://localhost:44059/dart_sdk.js:32521:48)
      at handleError (http://localhost:44059/dart_sdk.js:33070:51)
      at Function._propagateToListeners (http://localhost:44059/dart_sdk.js:33096:17)
      at _Future.new.[_completeError] (http://localhost:44059/dart_sdk.js:32943:23)
      at async._AsyncCallbackEntry.new.callback (http://localhost:44059/dart_sdk.js:32981:31)
      at Object._microtaskLoop (http://localhost:44059/dart_sdk.js:37794:13)
      at _startMicrotaskLoop (http://localhost:44059/dart_sdk.js:37800:13)
      at http://localhost:44059/dart_sdk.js:33309:9
  </code></pre>
  <p>Not realy sure what is actually causing the issue, hope you can help.
  Thank you so mush.</p>