Use Error.stack where available

git-svn-id: https://code.downthemall.net/repos/trunk@3669 43940e1f-b481-bb45-89eb-5c6a4bf3d40a
It is enough to call ensureWidgetPlacedInWindow

git-svn-id: https://code.downthemall.net/repos/trunk@3670 43940e1f-b481-bb45-89eb-5c6a4bf3d40a