decoder/ffmpeg: ignore empty packets
An empty packet would be a command for avcodec_send_packet() to finalize the codec. Fixes https://bugs.musicpd.org/view.php?id=4588
This commit is contained in:
An empty packet would be a command for avcodec_send_packet() to finalize the codec. Fixes https://bugs.musicpd.org/view.php?id=4588