Splits of very narrow nodes happen in wrong directions

[Adanos020]

Describe the bug
If a node you're splitting is narrow enough, the tab you're putting in it will not always be placed on the side you've picked. For example (shown below), if you have a very narrow tab on the right side of the DockArea and attempt to place another tab on its right hand side, it will instead land above it instead.

To Reproduce
Steps to reproduce the behavior:

1. Run the hello example
2. Move all tabs minus one to the right, so that the rightmost ones get very narrow (you may need shrink your application window to reproduce the exact conditions)
3. Try moving the last tab to the right hand side of the rightmost tab.
4. If the previously rightmost tab was narrow enough, the new tab will be inserted above it.

Expected behavior
In the example I've described, the tab should be placed on the right hand side, i.e. the side the user picked.

Screenshots