Same was true for SimpleDeform.
Invert vertex group influence should only have an effect if there is a
group specified.
Shrinkwrap always uses a weight (gets weights via
`BKE_defvert_array_find_weight_safe` -- which gets full weight for no
group specified, rightfully so), if this gets inverted, we get no
influence at all.
Now move the inverting of the weights to `BKE_defvert_array_find_weight_safe`,
adjust the other callers accordingly (Bevel also does not need to check for a valid
vertexgroup beforehand).
Pull Request: https://projects.blender.org/blender/blender/pulls/121625
a636b101d7