title: audio not send react-native-webrtc
body: <p>In prepareWebrtc function at the end I have the following code:</p>
  
  <pre><code>MediaStreamTrack.getSources(sourceInfos =&gt; {
    var isFront = camera_front
    console.log(sourceInfos);
    let videoSourceId;
    for (const i = 0; i &lt; sourceInfos.length; i++) {
      const sourceInfo = sourceInfos[i];
      if(sourceInfo.kind == "video" &amp;&amp;
         sourceInfo.facing == (isFront ? "front" : "back")) {
        videoSourceId = sourceInfo.id;
      }
    }
    console.log("videoSourceId:" + videoSourceId)
    getUserMedia({
      "audio": true,
      "video":false
    }, (stream) =&gt; {
      streamsDone(handleId, jsep, media, callbacks, stream)
    },
    // TODO: add error handling
    () =&gt; undefined
    );
  });
  </code></pre>
  
  <p>When "video" is true for android and when video is<code>{optional: [{sourceId: videoSourceId}] }</code> for ios, audio gets transmitted, however, then I have to ask for camera permissions which I don't want to do. When I do "video":false, audio can be received by my app; however, it doesn't get send. </p>