Fixes: Timeout (37sec -> 52ms)
Fixes: 18892/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_TARGA_fuzzer-5739537854889984

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