bug#45109: GNOME: unable to change alert "beep" sound since staging merge

[Mark H Weaver <mhw@netris.org>]

Since the recent merge of the 'staging' branch into 'master' on 28 Nov
2020, I'm no longer able to configure the alert sound in GNOME.  That's
a pity, since I find the default "drip" sound extremely unpleasant.

In more detail:

To configure the alert sound, I first open GNOME Settings by clicking on
the gear icon in the pull-down menu on the right side of GNOME Shell's
top bar.  From there, I navigate to the "Sound" section and scroll to
the bottom of that section, where I'm given a choice of 4 options for
the "Alert Sound".

For as long as I can remember, and even today, this pane *does* remember
my preferred Alert Sound (sonar), and correctly highlights it as my
selected choice.  However, the default "drip" sound is the one that is
actually used by applications, e.g. by GNOME Terminal and Emacs.

Note that even before the recent staging merge, periodically (maybe once
a week or so), I would log in and find that the dreaded "drip" sound was
being used as my alert sound.  Each time, I was able to fix it by going
back to the Sound section of GNOME Settings, and clicking again on my
preferred alert sound (although it was already selected as my configured
alert sound).  Now, since the recent staging merge, that no longer
works.

If anyone can suggest a way to successfully change my alert sound, I
would be grateful.

       Mark