Mistake in a0e6e16da5
Testing of the previous commit was inadequate, it works when a brush
tool is selected and invoked via the operator search, as the
`active_vert` property will be set by the raycast. When the Mask by
Color tool is actually active, the brush cursor, and thus the function
that performs a racyast is inactive, preventing the operator from
running.
Pull Request: https://projects.blender.org/blender/blender/pulls/134960
1bf6d78d18