Fixes: signed integer overflow: 1073750247 * 2 cannot be represented in type 'int'
Fixes: 70722/clusterfuzz-testcase-minimized-ffmpeg_dem_ASF_O_fuzzer-5447231587549184
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>