Fix Warning messages when closing About popup

There is a too agressive check in KWidgetItemDelegateEventListener that complains about
"User of KWidgetItemDelegate should not delete widgets created by createItemWidgets!"
when closing an about dialog.

I tried making it less agressive but since i could not, i'm just deleting things in a different order in the destruction of KAboutApplicationDialog so that the warning is not triggered and our users get angry
REVIEW: 105627

FIXED-IN: 4.9.1