More fixes

Signed-off-by: Mario Danic <mario@lovelyhq.com>

app/src/main/java/com/nextcloud/talk/activities/CallActivity.java

@@ -651,20 +651,23 @@ public class CallActivity extends AppCompatActivity {
         }
 
 
-        if (localMediaStream.videoTracks.size() > 0) {
+        if (localMediaStream.videoTracks != null && localMediaStream.videoTracks.size() > 0) {
             localMediaStream.removeTrack(localMediaStream.videoTracks.get(0));
         }
 
-        if (localMediaStream.audioTracks.size() > 0) {
+        if (localMediaStream.audioTracks != null && localMediaStream.audioTracks.size() > 0) {
             localMediaStream.removeTrack(localMediaStream.audioTracks.get(0));
         }
+        
         localVideoTrack = null;
         localAudioTrack = null;
         localRenderer = null;
         localMediaStream = null;
 
-        videoCapturer.dispose();
-        videoCapturer = null;
+        if (videoCapturer != null) {
+            videoCapturer.dispose();
+            videoCapturer = null;
+        }
 
         pipVideoView.release();