WallDrawer.draw() fixed.

cicaprojekt/WallDrawer.java

@@ -25,7 +25,7 @@ public class WallDrawer extends ImagePanel implements Drawer {
                 changeImage("RedStargate.png");
                 break;
             case "GreenStargate":
-                changeImage("GreenStargate");
+                changeImage("GreenStargate.png");
                 break;
             default:
                 changeImage("Wall.png");