OSV-2022-674 Use-of-uninitialized-value in cdef_filter_block_c

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=49787 Crash type: Use-of-uninitialized-value Crash state: cdeffilterblockc cdeffilterblock8x8c dav1dcdefbrow8bpc...