Fixes: 23721/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SCPR_fuzzer-5914074721550336

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit c8de8dfba6b2706f22214489b1779fb0d27e7e65)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>