Fixes: Timeout (158sec -> 36sec)
Fixes: 14214/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DSICINVIDEO_fuzzer-5633569034076160

This is untested with valid cin files as none of the files i found cover the changed
codepath

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>