Fixes: signed integer overflow: 2129689466 + 2129689466 cannot be represented in type 'int'
Fixes: 20715/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SONIC_fuzzer-5155263109922816

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 75d520e33704447f1b29ac47fd9e40994a6bc659)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>