lavf: always unref the packet passed to av_interleaved_write_frame() on error
Merge commit '394fb56c29eee7f4f8f0334d8b5d30d3c54ac703'

* commit '394fb56c29eee7f4f8f0334d8b5d30d3c54ac703':
  lavf: always unref the packet passed to av_interleaved_write_frame() on error

Merged-by: Michael Niedermayer <michaelni@gmx.at>
ffmpeg: fix vstats

Broken by: 394fb56c29eee7f4f8f0334d8b5d30d3c54ac703
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>