Remove parent on special case makes ui unusable
Submitted by Carlos Soriano
Given this: http://fpaste.org/114621/04220669/
It's GapplicationWindow -> scrolledWindow -> ViewPort -> ListBox.
I wanted to delete Viewport and ScrolledWindow, so I select listbox -> delete parent.
Then the view becomes unusable and the ui contains now: http://fpaste.org/114624/20962140/
And glade still shows the ListBox view as normal on the Widgets panel, but it's not shown on running state, and you cannot modify anything, even if I wanted to proceed deleting scrolledWindow I couldn't.