fix: flutter analyze issues

Author: jokerttu

example/lib/pages/poi_click.dart

@@ -27,7 +27,6 @@ class PoiClickPage extends ExamplePage {
 }
 
 class _PoiClickPageState extends ExamplePageState<PoiClickPage> {
-  GoogleMapViewController? _mapController;
   PointOfInterest? _lastClickedPoi;
 
   @override
@@ -105,7 +104,6 @@ class _PoiClickPageState extends ExamplePageState<PoiClickPage> {
   }
 
   Future<void> _onViewCreated(GoogleMapViewController controller) async {
-    _mapController = controller;
     await controller.setMyLocationEnabled(true);
   }
 
@@ -114,10 +112,4 @@ class _PoiClickPageState extends ExamplePageState<PoiClickPage> {
       _lastClickedPoi = poi;
     });
   }
-
-  @override
-  void dispose() {
-    _mapController = null;
-    super.dispose();
-  }
 }