Blender Git Loki

Fix T48186: Grease Pencil Smooth brush doesn't work properly - "erase" the stroke thickness

As soon as you started trying to smooth a stroke, the thickness of the stroke
would quickly drop right down to near zero, if "affect pressure" was enabled.

This step got accidentally missed when restoring the affect pressure functionality to
the stroke smoothing brush code, following cleanups from the stroke quality patch.