Fixes: 62276/clusterfuzz-testcase-minimized-ffmpeg_dem_RPL_fuzzer-4677434693517312
Fixes: signed integer overflow: 5555555555555555556 * 8 cannot be represented in type 'long long'

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