So that when it's destroyed, the internal ref becomes NULL and we then can safely call g_clear_pointer() on it. Closes: https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/1154
So that when it's destroyed, the internal ref becomes NULL and we then can safely call g_clear_pointer() on it. Closes: https://gitlab.gnome.org/GNOME/gnome-calendar/-/issues/1154