Comment 10 for bug 1653460

OK I can confirm this is cause by more dynamic layouts,
where w_ og h_ (would) become negative for a while.

Changing the Assertion will not help in this case.
I will try to add some minumu widht and height.

The Alternative would be to first layout() without assertions
and then check the layout later. (As of my experience this
will result in some ugly circular layout issues.