Merge pull request #96 from fengdai:release

PiperOrigin-RevId: 458883441
(cherry picked from commit 486c35045ddcf7a87b9df4d3674d6ee2de79aab7)

testutils/src/main/java/com/google/android/exoplayer2/testutil/StubPlayer.java

@@ -68,6 +68,7 @@ public class StubPlayer extends BasePlayer {
   }
 
   @Override
+  @Nullable
   public PlaybackException getPlayerError() {
     throw new UnsupportedOperationException();
   }