OSV-2020-188 Heap-buffer-overflow in BEInt<short, 2>::operator short

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=20924 Crash type: Heap-buffer-overflow READ 2 Crash state: BEInt::operator short OT::IntType::operator int OT::TupleVarHeader::calculatescalar...