OSV-2025-855 Use-of-uninitialized-value in AlphaReplace_SSE2

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=454314139 Crash type: Use-of-uninitialized-value Crash state: AlphaReplaceSSE2 WebPReplaceTransparentPixels WebPEncode...