Link the unlinked portal in purple room to itself in demo scene

src/app.cpp

@@ -68,6 +68,9 @@ App::App()
 	// bend hallway to purple
 	world_.LinkPortals(s4i, "EDoor", s5i, "Door1", 0);
 	world_.LinkPortals(s4i, "SDoor", s5i, "Door2", 0);
+
+	// purple to itself
+	world_.LinkPortals(s4i, "WDoor", s4i, "WDoor", 0);
 	
 	world_.Bake();