("important" because it's a crash, not RC because it's presumably not
happening for everyone.)

gnome-shell aborted abruptly, killing my session.

Feb 05 09:44:43 o gsd-media-keys[1118]: **
Feb 05 09:44:43 o gsd-media-keys[1118]: Gvc:ERROR:../subprojects/gvc/gvc-mixer-stream.c:535:gvc_mixer_stream_get_port: code should not be reached
Feb 05 09:44:43 o gsd-media-keys[1118]: Bail out! Gvc:ERROR:../subprojects/gvc/gvc-mixer-stream.c:535:gvc_mixer_stream_get_port: code should not be reached
Feb 05 09:44:43 o gnome-shell[999]: **
Feb 05 09:44:43 o gnome-shell[999]: Gvc:ERROR:../subprojects/gvc/gvc-mixer-stream.c:535:gvc_mixer_stream_get_port: code should not be reached
Feb 05 09:44:43 o gnome-shell[999]: Bail out! Gvc:ERROR:../subprojects/gvc/gvc-mixer-stream.c:535:gvc_mixer_stream_get_port: code should not be reached
Feb 05 09:44:43 o gnome-shell[999]: == Stack trace for context 0x565550cd9a90 ==
Feb 05 09:44:43 o gnome-shell[999]: #0   565550da64e8 i   resource:///org/gnome/shell/ui/init.js:21 (cdf9028d8d0 @ 48)

I had opened the menu in the upper right, and it crashed shortly after
that.

Did you perhaps connect a Bluetooth audio device, or do something
related to a Bluetooth audio device?
#1126514. I see you reported this against 49.3-2, but could it be the
case that 49.3-1 (or earlier) was still running since before you
upgraded, and then crashed in this way?

(I see that we might need
https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/4063 as a
follow-up fix, though.)

     smcv

I did have one connected at the time, yes.
gnome-shell to log the Debian package version.