Don't call doSomeWork if we're preparing

library/src/main/java/com/google/android/exoplayer/ExoPlayerImplInternal.java

@@ -525,7 +525,7 @@ import java.util.List;
         notifyAll();
       }
     }
-    if (state != ExoPlayer.STATE_IDLE) {
+    if (state != ExoPlayer.STATE_IDLE && state != ExoPlayer.STATE_PREPARING) {
       // The message may have caused something to change that now requires us to do work.
       handler.sendEmptyMessage(MSG_DO_SOME_WORK);
     }