title: Flutter 2.0 web version with firebase messaging is not working
body: <p>Flutter application is designed for mobile and web. We are using firebase_messaging for messaging funtioanlity. It was working charm earlier. Recently we upgraded our Flutter SDK to 2.0 version (Channel stable, 2.0.4).</p>
  <p>And the application works as like earlier in mobile version. But while executing in web version gives me the below mentioned error and was unable to solve.</p>
  <p>Following command already tried to disable null safety but no use.</p>
  <pre><code>flutter run --no-sound-null-safety
  </code></pre>
  <blockquote>
  <p>Error logs:</p>
  </blockquote>
  <pre><code>Debug service listening on ws://127.0.0.1:53789/y22KqzTNKwU=/ws
  
  Running with unsound null safety
  For more information see https://dart.dev/null-safety/unsound-null-safety
  Debug service listening on ws://127.0.0.1:53789/y22KqzTNKwU=/ws
  TypeError: Cannot read property 'isSupported' of undefined
      at new firebase_messaging_web.FirebaseMessagingWeb.new (http://localhost:53495/packages/firebase_messaging_web/firebase_messaging_web.dart.lib.js:189:51)
      at Function.registerWith (http://localhost:53495/packages/firebase_messaging_web/firebase_messaging_web.dart.lib.js:56:73)
      at Object.registerPlugins (http://localhost:53495/packages/pca_app/generated_plugin_registrant.dart.lib.js:44:49)
      at main (http://localhost:53495/web_entrypoint.dart.lib.js:44:35)
      at main.next (&lt;anonymous&gt;)
      at runBody (http://localhost:53495/dart_sdk.js:39051:34)
      at Object._async [as async] (http://localhost:53495/dart_sdk.js:39082:7)
      at main$ (http://localhost:53495/web_entrypoint.dart.lib.js:43:18)
      at http://localhost:53495/main_module.bootstrap.js:19:10
      at Array.forEach (&lt;anonymous&gt;)
      at window.$dartRunMain (http://localhost:53495/main_module.bootstrap.js:18:32)
      at &lt;anonymous&gt;:1:8
      at Object.runMain (http://localhost:53495/dwds/src/injected/client.js:8656:21)
      at http://localhost:53495/dwds/src/injected/client.js:22068:19
      at _wrapJsFunctionForAsync_closure.$protected (http://localhost:53495/dwds/src/injected/client.js:3830:15)
      at _wrapJsFunctionForAsync_closure.call$2 (http://localhost:53495/dwds/src/injected/client.js:10905:12)
      at Object._asyncStartSync (http://localhost:53495/dwds/src/injected/client.js:3794:20)
      at main__closure1.$call$body$main__closure (http://localhost:53495/dwds/src/injected/client.js:22080:16)
      at main__closure1.call$1 (http://localhost:53495/dwds/src/injected/client.js:22007:19)
      at StaticClosure._rootRunUnary [as call$2$5] (http://localhost:53495/dwds/src/injected/client.js:4153:16)
      at _CustomZone.runUnary$2$2 (http://localhost:53495/dwds/src/injected/client.js:12136:39)
      at _CustomZone.runUnaryGuarded$1$2 (http://localhost:53495/dwds/src/injected/client.js:12068:14)
      at _ControllerSubscription._sendData$1 (http://localhost:53495/dwds/src/injected/client.js:11697:19)
      at _DelayedData.perform$1 (http://localhost:53495/dwds/src/injected/client.js:11849:59)
      at _PendingEvents_schedule_closure.call$0 (http://localhost:53495/dwds/src/injected/client.js:11898:14)
      at Object._microtaskLoop (http://localhost:53495/dwds/src/injected/client.js:3990:24)
      at StaticClosure._startMicrotaskLoop (http://localhost:53495/dwds/src/injected/client.js:3996:11)
      at _AsyncRun__initializeScheduleImmediate_internalCallback.call$1 (http://localhost:53495/dwds/src/injected/client.js:10774:9)
      at invokeClosure (http://localhost:53495/dwds/src/injected/client.js:1250:26)
      at MutationObserver.&lt;anonymous&gt; (http://localhost:53495/dwds/src/injected/client.js:1269:18)
  </code></pre>
  <p>Flutter doctor report:</p>
  <pre><code>&gt; Doctor summary (to see all details, run flutter doctor -v): [√]
  &gt; Flutter (Channel stable, 2.0.4, on Microsoft Windows [Version
  &gt; 10.0.18363.1441], locale en-GB) [√] Android toolchain - develop for Android devices (Android SDK version 30.0.2) [√] Chrome - develop for
  &gt; the web [√] Android Studio (version 4.0) [√] VS Code (version 1.41.1)
  &gt; [√] Connected device (2 available)
  &gt; 
  &gt; • No issues found!
  </code></pre>