Fixes: 54979/clusterfuzz-testcase-minimized-ffmpeg_dem_AVR_fuzzer-6681035461230592
Fixes: Timeout

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegReviewed-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>