Use SafeNormalize for normals sampled from XYZ (non-DXT5nm/ASTCnm) no…

[hkr]

Purpose of this PR

Fix case 1351020

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Testing status

Manual

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Comments to reviewers

With 3 component normal maps it's easily possible to get near-zero-length normals after filtering.
Combined with normalization in fp16 this can cause sporadic Inf/NaN which then spreads with post processing effects like Bloom when rendering to a floating point framebuffer.
With DXT5nm this cannot happen because the decoding always makes sure that the length is 1.
It would probably be possible to sanitize normals during import but this is much easier and XYZ normal maps are legacy anyway.

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