Fixes: OOM
Fixes: 8781/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_JPEG2000_fuzzer-5810709081358336

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 0898a3d9)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>