Moved assignment of OverlayWindow.Owner to the Loaded event as an attempt to fix a CompositionException caused by trying to set the window's Owner to a framework element that has not yet been shown.
Moved assignment of OverlayWindow.Owner to the Loaded event as an attempt to fix a CompositionException caused by trying to set the window's Owner to a framework element that has not yet been shown.

SamHurne/gw2pao,StevenLiekens/gw2pao,kirkerafael/gw2pao