Heap-buffer-overflow in OT::Layout::GPOS_impl::PairSet<OT::Layout::MediumTypes>::apply
OSS-Fuzz report:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=55287
```
Crash type: Heap-buffer-overflow READ 1
Crash state:
OT::Layout::GPOS_impl::PairSet<OT::Layout::MediumTypes>::apply
OT::Layout::GPOS_impl::PairPosFormat1_3<OT::Layout::MediumTypes>::apply
bool OT::hb_accelerate_subtables_context_t::apply_to<OT::Layout::GPOS_impl::Pair
```