Don't throw an exeption when ESC[u used before ESC[s

This should fix error:
graphic.js line 395: TypeError: y is undefined

exec/load/graphic.js

 /*
  * "Graphic" object
  * Allows a graphic to be stored in memory and portions of it redrawn on command
+ * @format.tab-size 4, @format.use-tabs true
  */
 
 require("userdefs.js", "USER_ICE_COLOR");
@@ -326,7 +327,9 @@ Object.defineProperty(Graphic.prototype, "ANSI", {
 				saved={'x':x, 'y':y};
 			},
 			'u':function(params) {
+				if (saved.x !== undefined)
 					x = saved.x;
+				if (saved.y !== undefined)
 					y = saved.y;
 			}
 		};