fix lint issues and deprecated calls, format

Author: Illia Romanenko

flutter_vlc_player/example/lib/single_tab.dart

@@ -190,15 +190,15 @@ class _SingleTabState extends State<SingleTab> {
                         hwAcc: HwAcc.FULL);
                     break;
                   case VideoType.file:
-                    Scaffold.of(context).showSnackBar(
+                    ScaffoldMessenger.of(context).showSnackBar(
                       SnackBar(
                         content: Text('Copying file to temporary storage...'),
                       ),
                     );
                     await Future.delayed(Duration(seconds: 1));
                     var tempVideo = await _loadVideoToFs();
                     await Future.delayed(Duration(seconds: 1));
-                    Scaffold.of(context).showSnackBar(
+                    ScaffoldMessenger.of(context).showSnackBar(
                       SnackBar(
                         content: Text('Now trying to play...'),
                       ),
@@ -207,7 +207,7 @@ class _SingleTabState extends State<SingleTab> {
                     if (await tempVideo.exists()) {
                       await _controller.setMediaFromFile(tempVideo);
                     } else {
-                      Scaffold.of(context).showSnackBar(
+                      ScaffoldMessenger.of(context).showSnackBar(
                         SnackBar(
                           content: Text('File load error.'),
                         ),

flutter_vlc_player/example/lib/vlc_player_with_controls.dart

@@ -373,7 +373,7 @@ class VlcPlayerWithControlsState extends State<VlcPlayerWithControls>
   }
 
   void _togglePlaying() async {
-   _controller.value.isPlaying
+    _controller.value.isPlaying
         ? await _controller.pause()
         : await _controller.play();
   }
@@ -510,7 +510,7 @@ class VlcPlayerWithControlsState extends State<VlcPlayerWithControls>
       );
       await _controller.castToRenderer(selectedCastDeviceName);
     } else {
-      Scaffold.of(context)
+      ScaffoldMessenger.of(context)
           .showSnackBar(SnackBar(content: Text('No Display Device Found!')));
     }
   }

flutter_vlc_player/lib/src/vlc_player_controller.dart

@@ -846,7 +846,6 @@ class VlcPlayerController extends ValueNotifier<VlcPlayerValue> {
   /// [viewId] - the id of view that is generated by the platform
   /// This method will be called after the platform view has been created
   Future<void> onPlatformViewCreated(int viewId) async {
-    if (viewId == null) return;
     _viewId = viewId;
     // do we need to initialize controller after view becomes ready?
     if (autoInitialize) {