OSV-2020-2067 Heap-buffer-overflow in WelsDec::DecodeCurrentAccessUnit

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=26302 Crash type: Heap-buffer-overflow WRITE Crash state: WelsDec::DecodeCurrentAccessUnit WelsDec::ConstructAccessUnit WelsDecodeBs...