Blender Git Loki

Fix T74692: Do not draw nodes with the default face set

The default face set color is white, so we can skip drawing the default
face set. This allows to enable again the optimization of not drawing
overlays in nodes where the mask is empty.

This will still slow down the viewport when a new face set is created
for the whole mesh or when inverting the mask, like in previous
versions.

I also renamed the function to make more clear that now it is checking
for both mask and face sets.

Reviewed By: brecht

Maniphest Tasks: T74692

Differential Revision: https://developer.blender.org/D7207