the object in volume stack should be used instead of `isect.object`.
NOTE: this solution does not work for overlapping volumes. But since
light linking of overlapping volumes did not work before, it should be
fine to implement this partial solution. We read the bottom of the stack
instead of the top to avoid looping through the entire stack.
Pull Request: https://projects.blender.org/blender/blender/pulls/124341
204b99dd3f