Fixes: Timeout (18sec -> 0.4sec)
Fixes: 17585/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TRUEMOTION1_fuzzer-5117015135617024

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