Borders of panes are improperly updated when closing a pane #4057
Description
Simplest possible repro way:
- Split pane two times
- Close left-most pane
Effect: Right pane doesn't have any border, although it touches other pane (btw, this is also the repo for #3744).
This is because a remainingPane always clears the border that it got from split, even if it is still needed.
I've actually fixed this in my upcoming PR, I'm only filling this issue so I can mark it as closed ;)