Fixes: runtime error: signed integer overflow: -2049425300 + -117591631 cannot be represented in type 'int'
Fixes: part of 2096/clusterfuzz-testcase-minimized-4901566068817920

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