exwm--server-stop dumps core in exwm-28 on emacs-29.1

[franburstall]

Since upgrading to exwm-28, exwm--server-stop (called from kill-emacs-hook) causes emacs to dump core.

This happens reliably on both debian (bookworm) and arch.

Inspection of the backtrace in gdb shows that the proximate cause is the loss of the X11 connection causing emacs to abort. Perhaps this is related to the following:

Warning: due to a long standing Gtk+ bug
https://gitlab.gnome.org/GNOME/gtk/issues/221
Emacs might crash when run in daemon mode and the X11 connection is unexpectedly lost.

A workaround (probably unsatisfactory but it gets the rest of emacs-kill-hook run) is to simply remove it from the hook:

(remove-hook 'kill-emacs-hook #'exwm--server-stop)

Any idea what changed?

Happy to provide backtraces and further information.