message: Fix additional issue in ffmpeg 3.4 where cached packet should just ignore error
diff: @@ -111,6 +111,12 @@ bool VideoReader::ReadAhead(bool first)
  if (packet_.stream_index == stream_index_) {
  int got_frame = 0;
  int decoded = avcodec_decode_video2(codec_context_, frame_, &got_frame, &packet_);
  + if (!frame_more_ && got_frame) {
  + // This is the cached packet.
  + sws_scale(sws_context_, frame_->data, frame_->linesize, 0, codec_context_->height, frame_rgb_->data, frame_rgb_->linesize);
  + packet_more_ = true;
  + return true;
  + }
  if (decoded >= 0 && got_frame) {
  sws_scale(sws_context_, frame_->data, frame_->linesize, 0, codec_context_->height, frame_rgb_->data, frame_rgb_->linesize);
  if (packet_.data) {
  