Blender Git Loki

Fix T72690: Do not draw points behind the viewport camera in the paint cursor

In some situations the symmetry point may be behind the camera, so the
projection is inverted and it looks wrong. This avoids drawing points in
screen space when they are behind the camera.

Reviewed By: jbakker

Maniphest Tasks: T72690

Differential Revision: https://developer.blender.org/D6487