Small UX fix. When hidding everything but the active face set with H, the last stroke lotation center can be in a part of the model that is hidden, so viewport navigation becomes confusing until you start a new stroke on the visible face set. Now the viewport navigation rotation center is updated to the active vertex when using a visibility operation that uses it, so it always rotates using the visible face set as the origin. Reviewed By: jbakker Differential Revision: https://developer.blender.org/D7137