bug#23842: 24.4; Runaway background process

[Eli Zaretskii]

> From: Ken Brown <kbrown@cornell.edu>
> Date: Mon, 27 Jun 2016 09:24:06 -0400
> Cc: 23842@debbugs.gnu.org
> 
>      ;; Show possible completions in a temporary buffer.
>      (with-output-to-temp-buffer "*Completions*"
>        (display-completion-list allcomp))
>      ;; Wait for a key press. Then delete *Completion*  window
>      (momentary-string-display "" (point))
>      (delete-window (get-buffer-window (get-buffer "*Completions*")))))
> 
> It's hard to see how this could possibly work.  As soon as you click in 
> the *Completion* window, the window is deleted.

It could perhaps work if we didn't check the window for being a live
one.

Anyway, the code is definitely broken and should be fixed.