Update __chakraLibrary.CheckArrayAndGetLen to correctly check for null/undefined

Author: jackhorton

lib/Runtime/Library/JsBuiltIn/JsBuiltIn.js

@@ -193,13 +193,12 @@
         "use strict";
 
         if (__chakraLibrary.isArray(obj)) {
-            return { o: obj, len: obj.length }
-        }
-        else {
-            if (this === null || this === undefined) {
+            return { o: obj, len: obj.length };
+        } else {
+            if (obj === null || obj === undefined) {
                 __chakraLibrary.raiseThis_NullOrUndefined(builtInFunc);
             }
-            return { o: __chakraLibrary.Object(obj), len: __chakraLibrary.GetLength(obj) }
+            return { o: __chakraLibrary.Object(obj), len: __chakraLibrary.GetLength(obj) };
         }
     });