title: Flutter Provider (ChangeNotifierProxyProvider) failing because hasListeners is true
body: <p>I have suddenly got a problem with my providers in a quite big app. I've managed to trim it down to this minimal example:</p>
  <pre class="lang-dart prettyprint-override"><code>import 'package:flutter/material.dart';
  import 'package:provider/provider.dart';
  
  class AuthMock with ChangeNotifier {}
  
  class ProfileMock with ChangeNotifier {}
  
  void main() {
    runApp(
      ChangeNotifierProvider(
        create: (_) =&gt; AuthMock(),
        child: ChangeNotifierProxyProvider&lt;AuthMock, ProfileMock&gt;(
          create: (_) =&gt; ProfileMock(),
          lazy: false,
          update: (_, auth, profile) {
            return profile!;
          },
          child: Center(
            child: Text(
              'No crashy?',
              style: TextStyle(color: Colors.black),
              textDirection: TextDirection.ltr,
            ),
          ),
        ),
      ),
    );
  }
  </code></pre>
  <p>If you run this as-is, there's no problem: you get a white screen with &quot;No crashy?&quot; in the center.</p>
  <p><strong>However!</strong> If I add a <em>breakpoint</em> (in VS Code) on the <code>return profile!</code> line, I get the following error:</p>
  <pre><code>&quot;sv&quot;: 6 untranslated message(s).
  To see a detailed report, use the untranslated-messages-file
  option in the l10n.yaml file:
  untranslated-messages-file: desiredFileName.txt
  &lt;other option&gt;: &lt;other selection&gt;
  This will generate a JSON format file containing all messages that
  need to be translated.
  Launching lib/main.dart on Android SDK built for x86 in debug mode...
  lib/main.dart:1
  ✓  Built build/app/outputs/flutter-apk/app-debug.apk.
  Connecting to VM Service at ws://127.0.0.1:44893/hVEU7sS4XkU=/ws
  D/EGL_emulation(10820): eglMakeCurrent: 0xde22bb20: ver 2 0 (tinfo 0xd2bcf620)
  
  ════════ Exception caught by widgets library ═══════════════════════════════════
  The following assertion was thrown building _InheritedProviderScope&lt;ProfileMock?&gt;(dirty, dependencies: [_InheritedProviderScope&lt;AuthMock?&gt;], value: Instance of 'ProfileMock', listening to value):
  'package:provider/src/listenable_provider.dart': Failed assertion: line 94 pos 28: 'value.hasListeners != true': is not true.
  
  The relevant error-causing widget was
  _InheritedProviderScope&lt;ProfileMock?&gt;
  package:provider/src/inherited_provider.dart:161
  When the exception was thrown, this was the stack
  #2      new ListenableProxyProvider0.&lt;anonymous closure&gt;
  package:provider/src/listenable_provider.dart:94
  #3      _CreateInheritedProviderState.value.&lt;anonymous closure&gt;
  package:provider/src/inherited_provider.dart:765
  #4      _CreateInheritedProviderState.value
  package:provider/src/inherited_provider.dart:767
  #5      _InheritedProviderScopeElement.value
  package:provider/src/inherited_provider.dart:583
  #6      _InheritedProviderScopeElement.build
  package:provider/src/inherited_provider.dart:537
  ...
  ════════════════════════════════════════════════════════════════════════════════
  </code></pre>
  <p>I'm really not sure what I'm doing wrong. I've tested this on two computers (one Mac, one Linux). I'm using provider package version 6.0.0, but the same problem is present with 5.0.0. I have so far only tested with Android.</p>
  <p>I've validated that the error happens with a new app as well, created with <code>flutter create</code> and the content of <code>main.dart</code> replaced with the above.</p>
  <p><code>flutter doctor</code> output:</p>
  <pre><code>[✓] Flutter (Channel stable, 2.2.0, on Linux, locale en_US.UTF-8)
  [✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
  [✓] Chrome - develop for the web
  [✓] Android Studio (version 3.6)
  [✓] VS Code (version 1.59.1)
  [✓] Connected device (2 available)
  
  • No issues found!
  </code></pre>
  <p>Any ideas?</p>