Clamp NaN to white when converting to integer #1709

Job	Run time
Fuzz targets (afl)	2m 7s
build_benchmarks	46s
cargo-deny	17s
Fuzz targets (cargo-fuzz)	51s
cargo-semver-checks	27s
clippy	2m 3s
public_private_dependencies	23s
rustfmt	5s
test_avif_decoding	1m 24s
test_other_archs (powerpc-unknown-linux-gnu)	2m 44s
test_other_archs (i686-unknown-linux-gnu)	1m 34s
test_features	40s
test_toolchains (1.70.0)	34s
test_features (default)	1m 58s
test_toolchains (nightly)	1m 50s
test_features (rayon)	34s
test_toolchains (beta)	1m 44s
test_features (avif)	1m 0s
test_features (bmp)	28s
test_features (dds)	29s
test_features (exr)	59s
test_features (ff)	33s
test_features (gif)	28s
test_features (hdr)	31s
test_features (ico)	43s
test_features (jpeg)	43s
test_features (png)	34s
test_features (pnm)	43s
test_features (qoi)	1m 4s
test_features (tga)	42s
test_features (tiff)	42s
test_features (webp)	33s
	30m 13s

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