Fix crash on wayland logout if xwayland hasn't started yet

If xwayland hasn't started yet then the root window id is 0, which is
invalid, so we crash in e_comp_x_shutdown.

src/modules/xwayland/e_mod_main.c

@@ -452,7 +452,7 @@ xwl_shutdown(void)
    if (exs->sig_hdlr) ecore_event_handler_del(exs->sig_hdlr);
 
    free(exs);
-   e_comp_x_shutdown();
+   if (e_comp_util_has_x()) e_comp_x_shutdown();
    ecore_x_shutdown();
    e_util_env_set("DISPLAY", NULL);
 }