Fixes: 644/clusterfuzz-testcase-4726434209726464
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/targets/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 6179dc8a)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>