Re-add missing return in RegisterExternalDecoder.

webrtc/modules/video_coding/video_receiver.cc

Index: webrtc/modules/video_coding/video_receiver.cc
diff --git a/webrtc/modules/video_coding/video_receiver.cc b/webrtc/modules/video_coding/video_receiver.cc
index e2720f685bfa3d2ea227b15e661b257f4e64167a..c347baa7b809ba34a44a239fe34d1d04919d10b1 100644
--- a/webrtc/modules/video_coding/video_receiver.cc
+++ b/webrtc/modules/video_coding/video_receiver.cc
@@ -245,6 +245,7 @@ void VideoReceiver::RegisterExternalDecoder(VideoDecoder* externalDecoder,
     // Make sure the VCM updates the decoder next time it decodes.
     _decoder = NULL;
     RTC_CHECK(_codecDataBase.DeregisterExternalDecoder(payloadType));
+    return;
   }
   _codecDataBase.RegisterExternalDecoder(externalDecoder, payloadType,
                                          internalRenderTiming);