avformat/movenc: Do not pass AVCodecParameters in avpriv_request_sample

      Fixes: out of array read
Fixes: ffmpeg_crash_8.avi

Found-by: Thuan Pham, Marcel Böhme, Andrew Santosa and Alexandru Razvan Caciulescu with AFLSmart
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>