Fixes: Timeout (100sec -> 0.7sec)
Fixes: 8668/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_G2M_fuzzer-5174143888130048

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 61dd2e07)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>