message: videoio(ffmpeg): fix handling of AVERROR_EOF
  decoder should be properly flushed after that
diff: @@ -1215,9 +1215,20 @@ bool CvCapture_FFMPEG::grabFrame()
  #endif
  int ret = av_read_frame(ic, &packet);
  - if (ret == AVERROR(EAGAIN)) continue;
  - /* else if (ret < 0) break; */
  + if (ret == AVERROR(EAGAIN))
  + continue;
  +
  + if (ret == AVERROR_EOF)
  + {
  + if (rawMode)
  + break;
  +
  + // flush cached frames from video decoder
  + packet.data = NULL;
  + packet.size = 0;
  + packet.stream_index = video_stream;
  + }
  if( packet.stream_index != video_stream )
  {
  