OSV-2026-1294 UNKNOWN WRITE in av1_cdef_mse_calc_frame_mt

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=562150738 Crash type: UNKNOWN WRITE Crash state: av1cdefmsecalcframemt av1cdefsearch encodewithrecodeloopandfilter...