bug#24213: 25.1.50; Fishy use of delete-window in register.el

[martin rudalics]

> The window is created by `display-buffer-below-selected' so we know its
> ours and thus delete-window is technically safe here. Use
> quit-window/quit-windows-on is ok as well for being defensive.
>
> Martin,
>
> it seems the documentation of display-buffer-below-selected isn't clear
> that it only reuses a window if it displays BUFFER already.

Indeed.  I tried to correct that on master, please have a look.  Note
that if there is a non-dedicated window below the selected one showing
some other buffer, that window may get used and is strictly spoken not
"ours".  Hopefully, ‘quit-window’ does not delete it.

martin