Wrong width of property editor

1. Open a file with a Rectangle item in Design mode.
2. Select the Rectangle item.
   The Properties editor is too wide for its view. Creator displays scrollbars:
   
3. Try to get rid of the scrollbars by making the view wider.
   The Properties editor grows, so the scrollbars stay the same:
   

Since the Properties editor can change its size, it should get the size of the view.