Fixes: index 32 out of bounds for type 'int [32]'
Fixes: 18350/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_ATRAC3P_fuzzer-5643794862571520

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