calculate contour if contour==true

examples/maze/maze_masking.scad

@@ -35,12 +35,12 @@ module maze_masking(start, mask, block_width, wall_thickness, wall_height, base_
 		mz_initialize(mask = mask)
     );
 	
-	pts = vx_contour([
+	pts = contour ? vx_contour([
 	for(y = [0:rows - 1])
 	    for(x = [0:columns - 1])
 		    if(mask[y][x] == 1)
 			    [x, rows - y - 1]
-	]);	
+	]) : [];	
 	
     walls = mz_square_walls(blocks, rows, columns, block_width);