Do not use Application.Current.MainWindow

[Michael Dietrich]

DragDrop.CreateDragAdorner uses Application.Current.MainWindow if the current element is not hosted directly in a window. Never ever try to guess the correct window by such APIs, this will fail everytime, please simply remove this and return null.

[Michael Dietrich]

I think this issue goes hand in hand with #165

[Jan Karger ツ ☀]

@FrecherxDachs changed with 0f56678