bug fixes for android auto

lib/streaming_audio_business_object.dart

@@ -10,10 +10,6 @@ enum StreamingPlaybackStatus { stopped, buffering, playing }
 
 class StreamingAudioBusinessObject extends ChangeNotifier {
   StreamingAudioBusinessObject() {
-    if (_audioHandler == null && _audioHandlerInitFuture == null) {
-      initializeBackgroundAudio();
-    }
-
     final initFuture = _audioHandlerInitFuture;
     if (initFuture != null) {
       initFuture.then((handler) {
@@ -74,6 +70,10 @@ class StreamingAudioBusinessObject extends ChangeNotifier {
   String get currentTitle => _currentTitle;
   String get currentSubtitle => _currentSubtitle;
 
+  Future<void> ensureInitialized() async {
+    await initializeBackgroundAudio();
+  }
+
   StreamingPlaybackStatus _mapPlaybackStateToStatus(PlaybackState state) {
     if (state.processingState == AudioProcessingState.completed) {
       return StreamingPlaybackStatus.stopped;