bug#48367: 28.0.50; quit-restore-buffer may jam

[martin rudalics]

> The first patch adress this, and a similar one : when there is a 
previous-buffer available, but it referes to the same buffer. (eg: try the recipe 
again but exchange the role of *Messages* and *Backtrace*, you will finish with a 
blank buffer for backtrace, that you can quit again to end up to the same point)
>
> The second patch is a proposition to clarify a little the code.

LGTM.  Can you please provide a ChangeLog entry and add a short comment
in the code that mentions the bug number of your report.

Also, have you signed the copyright agreement for Emacs?  How should I
call you in the commit?  "pillule"?

And please try to avoid putting your local settings in diffs as with

--- /usr/share/emacs/28.0.50/lisp/window.el.gz
+++ /home/user/src/patches/window.el

Many thanks, martin