The reason for this change is that the default ctor of KWindowInfo
creates a broken object. Calling any method in it will result in a
crush. Thus it is scheduled for removal in kwindowsystem framework
causing this code to no longer compile.
The solution is to use a pointer and set it to null as long as the
window has not been detected yet. To ensure that this doesn't fail
badly an assert is added to the getter in DetectWidget.
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