Fix `VMobject.add_points_as_corners()` to return `self` and safely handle empty `points` parameter#4091

chopan050 merged 3 commits intoManimCommunity:mainManimCommunity/manim:mainfrom

chopan050:fix-vmob-add-points-as-cornerschopan050/manim:fix-vmob-add-points-as-cornersCopy head branch name to clipboard