It is possible for a vertex to be processed by some function that
attempts to calculate the average of an attribute of all neighboring
elements when all elements are hidden. This results in NaN when using
`math::rcp` for the size of the related indices.
This commit switches the `rcp` call for the safe variant and removes an
invalid assert that previously existed.
Further cleanup to consolidate the various different average methods
will occur in the main branch (e.g. the `check_loose` and `interior`
functions)
Pull Request: https://projects.blender.org/blender/blender/pulls/140569
41d8066b1e