OSV-2020-1172 Global-buffer-overflow in WelsDec::ParseInterBInfo

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=12652 Crash type: Global-buffer-overflow READ 1 Crash state: WelsDec::ParseInterBInfo WelsDec::WelsActualDecodeMbCavlcBSlice WelsDec::WelsDecodeMbCavlcBSlice...