Fixes: runtime error: signed integer overflow: 161 * 13872281 cannot be represented in type 'int'

Fixes: 3295/clusterfuzz-testcase-minimized-4738998142500864

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