fix disposing Broadcast Sharing stream [#1108](https://github.com/flutter-webrtc/flutter-webrtc/issues/1108) (#1130)
fix disposing Broadcast Sharing stream [#1108](https://github.com/flutter-webrtc/flutter-webrtc/issues/1108) (#1130)

Co-authored-by: tatanka987 <78c743db92b98ad1f0c1d4f381481a707d7ed125@gmail.com>
flutter-webrtc/flutter-webrtc,flutter-webrtc/flutter-webrtc,flutter-webrtc/flutter-webrtc,flutter-webrtc/flutter-webrtc,flutter-webrtc/flutter-webrtc,flutter-webrtc/flutter-webrtc,flutter-webrtc/flutter-webrtc,flutter-webrtc/flutter-webrtc