Using iterator pattern instead of List::Element *.

Co-authored-by: Adam Scott <ascott.ca@gmail.com>

scene/resources/2d/navigation_polygon.cpp

@@ -396,9 +396,7 @@ void NavigationPolygon::make_polygons_from_outlines() {
 	vertices.clear();
 
 	HashMap<Vector2, int> points;
-	for (List<TPPLPoly>::Element *I = out_poly.front(); I; I = I->next()) {
-		TPPLPoly &tp = I->get();
-
+	for (const TPPLPoly &tp : out_poly) {
 		Vector<int> p;
 
 		for (int64_t i = 0; i < tp.GetNumPoints(); i++) {