OSV-2020-2093 Heap-buffer-overflow in ExpandPictureChroma_c

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=26570 Crash type: Heap-buffer-overflow WRITE 8 Crash state: ExpandPictureChromac ExpandReferencingPicture WelsDec::WelsCheckAndRecoverForFutureDecoding...