Gtk::GLArea throws "Couldn't find current GLX or EGL context.\n"' on unrealizing

[Gerlof Fokkema <gerlof fokkema gmail com>]

Dear list,

I'm trying to use Gtk::GLArea in a project of mine according to the
example provided online:
https://gitlab.gnome.org/GNOME/gtkmm/blob/master/demos/gtk-demo/example_glarea.cc

The OpenGL context activates and can be drawn onto no problem.
However, when exiting the application the following error is logged to console:

> a.out: ../libepoxy/src/dispatch_common.c:863: epoxy_get_proc_address: Assertion `0 && "Couldn't find 
> current GLX or EGL context.\n"' failed.

This gist contains about as little code as possible to reproduce the issue:
https://gist.github.com/gfokkema/a0c73de5c9df476b5b31057ebb63394f


To rule out mistakes in using gtkmm on my part I've tried compiling
and running the example_glarea.cc example linked above as well.
This results in the same error on exit:
┌─gerlof@gerlof-laptop ~/gtkmm/demos/gtk-demo (gtkmm-3-24 u=) $
└─╼g++ $(pkg-config --cflags --libs gtkmm-3.0) -lepoxy example_glarea.cc main.cc
┌─gerlof@gerlof-laptop ~/gtkmm/demos/gtk-demo (gtkmm-3-24 u=) $
└─╼./a.out
a.out: ../libepoxy/src/dispatch_common.c:863: epoxy_get_proc_address:
Assertion `0 && "Couldn't find current GLX or EGL context.\n"' failed.
Aborted (core dumped)

Software versions:
gtk: 3.24.13
gtkmm-3.0: 3.24.2
libepoxy: 1.5.4

Unfortunately I'm not really sure how to go about this issue, since I
ran into this whilst teaching myself gtkmm.
Can someone confirm this is unexpected behaviour, and if so, whether
it is an issue with gtkmm or with libepoxy?

Thanks in advance!

Kind regards,

Gerlof Fokkema