fixed realAdvanced menu

Console.java

@@ -99,8 +99,10 @@ public class Console {
                 }else if (mode.equals("5")){
                     advAnswer = advCalc.absoluteValue(advInput1);
 
-                }else {
+                }else if (mode.equals("6")) {
                     break;
+                }else{
+                    Console.println("Invalid input");
                 }
 
                 Console.println(Double.toString(advAnswer));