MahApps/MahApps.Metro — pull request #700 by thoemmi (2013-10-13 20:55:48+00:00)
Title: BorderlessWindowBehavior should not throw on missing parts

Currently `BorderlessWindowBehavior` throws NREs if the associated window is a `MetroWindow`, but is missing a `PART_TitleBar` or `PART_WindowCommands` element.