Fixes: signed integer overflow: 2147483424 * 2 cannot be represented in type 'int'
Fixes: 62276/clusterfuzz-testcase-minimized-ffmpeg_dem_WSVQA_fuzzer-4576211411795968

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