updated lookups to return undefined entry if invalid

tests/sprint2/test/test_carls_mistake.alpha

@@ -18,10 +18,10 @@ bar2 as (r,s) := {
 entry(arg) := {
  	   [ integer: result ; rec: w]
  	   result := foo(5);
- 	   w := reserve(w); (* see types.alpha – reserve returns a value of type address, which can be assigned to array and record variables*)
+ 	   w := reserve w; (* see types.alpha – reserve returns a value of type address, which can be assigned to array and record variables*)
 	   w.x := 5;
  	   w.y := 7;
  	   result := bar1(w); (* pass w (a rec type value) to bar1 *)
  	   result := bar2(5,7); (* implicitly build a rec type value, assign 5 and 7 to fields x and y, but call them r and s *)
  	   return 0;
-}
+}