Fixes NaN in Vector Displacement node caused by the normalization of
0, 0, 0 vectors.
This fixes both visual rendering issues and an "illegal address" error
on the GPU. The "illegal address" error came from the Light Tree
Sampling code not handling the NaN normals well, leading to weird code
paths being taken, eventually leading to a kernel_assert and a
user facing illegal address error.
In Blender 3.5+, this fixes two errors (visual artifacts and errors on
the GPU when using the light tree). In Blender 3.3 it only fixes one
(visual artifacts) because 3.3 doesn't have the light tree. The commit
message should be adjusted to represent that
Pull Request: blender/blender#111294
Alaska
ee2e231adc