OSV-2018-185 Heap-buffer-overflow in BEInt<unsigned short, 2>::operator unsigned short

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=11001 Crash type: Heap-buffer-overflow READ 1 Crash state: BEInt::operator unsigned short OT::IndexSubtable::getextents OT::IndexSubtableRecord::getextents...