OSV-2025-819 Use-of-uninitialized-value in HasAlpha32b_SSE2

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=449546226 Crash type: Use-of-uninitialized-value Crash state: HasAlpha32bSSE2 WebPPictureHasTransparency VP8LEncodeImage...