Fixes: shift exponent 4294967163 is too large for 32-bit type 'int'
Fixes: 41449/clusterfuzz-testcase-minimized-ffmpeg_IO_DEMUXER_fuzzer-6183636217495552
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Tomas Härdin <tjoppen@acc.umu.se>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>