add a fast return to the already a triangle case

Author: madhephaestus

src/main/java/eu/mihosoft/vrl/v3d/ext/org/poly2tri/PolygonUtil.java

@@ -594,6 +594,10 @@ public static ArrayList<Polygon> triangulatePolygon(Polygon incoming) throws Col
 			return result;
 		if (incoming.getVertices().size() < 3)
 			return result;
+		if (incoming.getVertices().size() == 3) {
+			result.add(incoming);
+			return result;
+		}
 		Polygon tmp = incoming;
 		Vector3d normalOfPlane = incoming.getPlane().getNormal().clone();
 		normalOfPlane.normalize();