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.
This is the same change as done for kcm kwinrules. And here we se
why copying code is bad ;-)
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