Fix: poisoned next function in "IteratorClose is called when reference evaluation produces a "return" completion". Fixes gh-670

src/dstr-assignment/array-rest-iter-rtrn-close.case

@@ -45,6 +45,9 @@ var thisValue = null;
 var args = null;
 var iterable = {};
 var iterator = {
+  next() {
+    throw new Test262Error();
+  },
   return: function() {
     returnCount += 1;
     thisValue = this;