OSV-2021-1606 Segv on unknown address in jxl::N_AVX2::SingleFromSingle

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=41233 Crash type: Segv on unknown address Crash state: jxl::NAVX2::SingleFromSingle jxl::ThreadPool::SequentialRunnerStatic jxl::ModularFrameDecoder::ModularImageToDecodedRect...