OSV-2021-1011 Use-of-uninitialized-value in jxl::N_AVX2::AddNoise

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=36158 Crash type: Use-of-uninitialized-value Crash state: jxl::NAVX2::AddNoise jxl::FinalizeImageRect jxl::ThreadPool::RunCallStatejxl::FinalizeFrameDecoding...