xwayland: Remove transform listener when destroying the wm

Fix a segfault occuring after the last X window was closed.
diff --git a/src/xwayland/window-manager.c b/src/xwayland/window-manager.c
index 74fba47..257c108 100644
--- a/src/xwayland/window-manager.c
+++ b/src/xwayland/window-manager.c
@@ -1801,6 +1801,7 @@
 	wl_list_remove(&wm->selection_listener.link);
 	wl_list_remove(&wm->activate_listener.link);
 	wl_list_remove(&wm->kill_listener.link);
+	wl_list_remove(&wm->transform_listener.link);
 
 	free(wm);
 }