fix analyze warnings

lib/src/participant/local_participant.dart

@@ -76,9 +76,6 @@ class LocalParticipant extends Participant {
       var trackInfo = await _engine.addTrack(
           cid: track.getCid(), name: track.name, kind: track.kind);
       var stream = await getMediaStream();
-      if (stream == null) {
-        return Future.error(TrackPublishError());
-      }
       var transceiverInit = new RTCRtpTransceiverInit(
         direction: TransceiverDirection.SendOnly,
         streams: [stream],

test/livekit_client_test.dart

@@ -1,7 +1,5 @@
 import 'package:flutter_test/flutter_test.dart';
 
-import 'package:livekit_client/livekit_client.dart';
-
 void main() {
   test('placeholder', () {});
 }