avcodec/shorten: Sanity check nmeans
Fixes: OOM
Fixes: 8195/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_SHORTEN_fuzzer-
5179785826271232
The reference software appears to use longs for 32bits and it uses int for nmeans
hinting that the intended maximum size was not 32bit.
Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit
d91a0b503d7a886587281bc1ee42476aa5e89f85)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>