Vertical docking is broken

Summary:

... (write here)

Steps to reproduce:

• open Inkscape
• dock on deialog
• docker second dialog under the first one

What happened?

• the dock is hidden only handed is visible
• handed does not work and does not rescale dialog

inkscape_gXa9f6NIP7

What should have happened?

• dock should be visible and take 50% of dock

Sample attachments:

preferences.xmldialogs-state.inidialogs-state-ex.ini

Version info

1.3 A