Docking above right toolbar not possible

Docking toolbar above right toolbar isn't possible if the right toolbar has only 3 or less tools in it.
Use attached example application to reproduce the issue:

1. Dock the toolbar with 4 toolbuttons to the right area.
2. Dock the toolbar with 3 toolbuttons so that two rows of toolbars are docked to the top.
3. Dock the toolbar with 2 toolbuttons to the right toolbar. Dock it above it the toolbar with 4 buttons.
   (Note that this works)
4. Now try swap the toolbars by docking the toolbar with 4 toolbuttons to be above the toolbar docked in step 3.
   => Observe that the toolbar with 4 toolbuttons can only be docked below the toolbar with 2 buttons, while the toolbar with 2 buttons can be docked both above and below the toolbar with 4 buttons.