Harden peer connection factory

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

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

@@ -552,6 +552,7 @@ public class CallActivity extends AppCompatActivity {
         PeerConnectionFactory.InitializationOptions initializationOptions = PeerConnectionFactory.InitializationOptions
                 .builder(this)
                 .setEnableVideoHwAcceleration(true)
+                .setFieldTrials(null)
                 .createInitializationOptions();
         PeerConnectionFactory.initialize(initializationOptions);
 
@@ -999,6 +1000,11 @@ public class CallActivity extends AppCompatActivity {
             localRenderer = null;
             localMediaStream = null;
 
+            if (peerConnectionFactory != null) {
+                peerConnectionFactory.dispose();
+                peerConnectionFactory = null;
+            }
+
             if (videoCapturer != null) {
                 videoCapturer.dispose();
                 videoCapturer = null;