Override width/height specifier not updating correctly

The Override width/height spinboxes should contain a default size when the root item does not have a size.
When commenting the size of the root item out, this is not properly updated.

To reproduce:
1) Create a project with a rectangle as root item.
2) Set the size to something and take a look at the 2D view.
3) If Override width/height contain values remove them.
3) Now comment the width and height statements out in the code view
4) Look at the 2D view. The rectangle does not show up since the override width/height spinboxes are empty