title: The argument type 'ModalRoute<Object?>?' can't be assigned to the parameter type 'PageRoute<dynamic>'
body: <p>Recently I am migrating to null safety. Updated the firebase_analytics: ^8.0.2.</p>
  <p>Now facing problem with this.observer.subscribe(this, ModalRoute.of(context)); Can some one help what to pass second argument.</p>
  <pre><code>class _BookedClassDetailsPageState extends 
  State&lt;BookedClassDetailsPage&gt; with SingleTickerProviderStateMixin, RouteAware{
  
  late FirebaseAnalyticsObserver observer;
  
  @override
  void initState() {
   super.initState();
   observer=widget.repository.analyticsService.getAnalyticsObserver();
   observer.analytics.setCurrentScreen(
       screenName: 'Booked Class Page',
       screenClassOverride: 'BookedClassPage'
   );
  
  }
  
  @override
  void didChangeDependencies() {
    super.didChangeDependencies();
    observer.subscribe(this, ModalRoute.of(context));
  }
   @override
   void dispose() {
      observer.unsubscribe(this);
      super.dispose();
   }
  }
  </code></pre>