Merge pull request #1902 from Ping20002015/master

Fix NPE for issue #1901

app/src/main/java/org/schabi/newpipe/player/BasePlayer.java

@@ -1134,6 +1134,7 @@ public abstract class BasePlayer implements
     }
 
     public boolean isPlaying() {
+        if (simpleExoPlayer == null) return false;
         final int state = simpleExoPlayer.getPlaybackState();
         return (state == Player.STATE_READY || state == Player.STATE_BUFFERING)
                 && simpleExoPlayer.getPlayWhenReady();