Scenes that only uses a world probe would didn't work. Raytracing
would look for the closest light probe, didn't find any and shader
would use undefined behavior to sample in the reflectionProbes texture.
In some cases this resulted in correct results when the world was
located on layer 0 with subdivision 0. In any other case this would
sample incorrect incoming light what lead to black reflections.
This PR fixes this by returning the world probe when no nearest light
probe cound be found.
Pull Request: https://projects.blender.org/blender/blender/pulls/112893
8f9c14145e