Fixes: index 26981 out of bounds for type 'ASFStreamData [128]'
Fixes: 27334/clusterfuzz-testcase-minimized-ffmpeg_dem_ASF_O_fuzzer-6197611002068992

Alternatively the array could be increased in size or the cases not fitting be ignored

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