Out-of-bounds read in core image-sequence parsing: a malformed HEIF
sequence with stco.entry_count == 0 and saiz.sample_count > 0 drives
SampleAuxInfoReader to dereference an empty chunks[0]. This sequence /
ISOBMFF track parsing (SampleAuxInfoReader, Box_saiz/saio/stco,
TrackBox/MovieBox) was added in v1.20.0. v1.19.8 — the version we
ship — has no track parsing at all, so the vulnerable code is not
present (verified: none of those symbols exist in the v1.19.8 source).