OSV-2020-1312 Use-of-uninitialized-value in FilterInput8bitWithStride_c

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=13004 Crash type: Use-of-uninitialized-value Crash state: FilterInput8bitWithStridec McHorVer20c McHorVer30c...