Criticals when running the app
(org.gnome.GamesDevel:2): Gtk-CRITICAL **: 21:52:09.250: _gtk_css_image_compute: assertion 'GTK_IS_CSS_IMAGE (image)' failed
(org.gnome.GamesDevel:2): GLib-GObject-CRITICAL **: 21:52:09.250: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
(org.gnome.GamesDevel:2): Gtk-CRITICAL **: 21:52:09.263: _gtk_css_image_compute: assertion 'GTK_IS_CSS_IMAGE (image)' failed
(org.gnome.GamesDevel:2): GLib-GObject-CRITICAL **: 21:52:09.264: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
(org.gnome.GamesDevel:2): Gtk-CRITICAL **: 21:52:09.303: _gtk_css_image_compute: assertion 'GTK_IS_CSS_IMAGE (image)' failed
(org.gnome.GamesDevel:2): GLib-GObject-CRITICAL **: 21:52:09.303: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
(org.gnome.GamesDevel:2): Gtk-CRITICAL **: 21:52:09.420: _gtk_css_image_compute: assertion 'GTK_IS_CSS_IMAGE (image)' failed
(org.gnome.GamesDevel:2): GLib-GObject-CRITICAL **: 21:52:09.421: g_object_unref: assertion 'G_IS_OBJECT (object)' failed
I suppose they have to do something with threaded loading.