Heap-memory write in FFMPEG

A heap out-of-bounds memory write exists in FFMPEG since version 5.1. The size calculation in `build_open_gop_key_points()` goes through all entries in the loop and adds `sc->ctts_data[i].count` to `sc->sample_offsets_count`. This can lead to an integer overflow resulting in a small allocation with `av_calloc()`. An attacker can cause remote code execution via a malicious mp4 file. We recommend upgrading past commit c953baa084607dd1d84c3bfcce3cf6a87c3e6e05