Detaching rightmost tab in a stack leads to duplicate ghost titlebar

[haiclu]

Version: Haiku shredder 1 hrev57151 x86_64 emulated with QEMU

Steps to reproduce:

1. open 2 or more windows
2. stack them
3. activate the rightmost tab (so it's yellow)
4. hold OPT and drag it in a south-west direction, detaching it

4.1 the direction is important because otherwise you draw over the dead region

5. Observe that the old window still has a tab decoration for the now detached tab.
6. Observe that when you drag the old window to the south west, the tab visual stays in place.

The ghost tab has to be manually painted over by e.g. dragging something over it.

This bug does not happen when detaching the active tab (yellow) in the middle, or when detaching any grey tab, even the rightmost one.

See attached video.

[haiclu]

Showing the bug

[humdinger]

This is actually a duplicate of #16006. But since this ticket has a more elaborate description and a nice small video, let's keep this one. :)

BTW, please leave the "keyword" of the ticket empty. It's meant for the devs to fill, mostly to group similar issues.