Fixes: Infinite loop
Fixes: 33958/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_THP_fuzzer-6590264069193728
Fixes: 33981/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_JPEGLS_fuzzer-5343224173559808
Fixes: 33986/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MJPEG_fuzzer-6598815122587648
Fixes: 34001/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SMVJPEG_fuzzer-6171098111672320

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