Fixes: -2.21166e+304 is outside the range of representable values of type 'long'
Fixes: 29169/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5725452796821504

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