avcodec/utils: Check block_align
Fixes: out of array access
Fixes: 18432/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMAV2_fuzzer-
5675574936207360
Fixes: 18326/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMAV2_fuzzer-
5071752362721280
Fixes: 18384/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_WMAV1_fuzzer-
5769439500304384
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>