OSV-2020-674 Heap-buffer-overflow in ihevcd_mv_merge

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=17196 Crash type: Heap-buffer-overflow READ 4 Crash state: ihevcdmvmerge ihevcdgetmvctb ihevcdparseslicedata...