Introduced in 750e3a6fba
The commit above incorrectly passes the `grids` `Span` into the
`calc_front_face` function, causing the calculation to miss vertices in
certain cases, as the function attempts to index instead of reading the
`normals` `Span` directly.
This has the potential to cause crashes too, as the indices of the grid
are not guaranteed to be bounded by the size of the `factors` array.
Pull Request: https://projects.blender.org/blender/blender/pulls/131886