calvin-li

The [joincall()](https://github.com/digitallysavvy/android-video-chat-demo/blob/a9dad9812de2cd423984a18c82f5050d6e21e671/app/src/main/java/com/example/android/myagoraapplication/MainActivity.java#L166) usage in `MainActivity.java` just has `null` in the place of the token. The app fails silently with a black screen for local stream, blank screen for remote stream.