`Array.prototype[Symbol.iterator] = null` stalls the process

```js
Array.prototype[Symbol.iterator] = null;
String.prototype[Symbol.iterator] = null;

test('test', () => {});
```

will never finish running until interrupted.

<img width="1371" alt="screen shot 2017-06-21 at 8 02 56 pm" src="https://user-images.githubusercontent.com/940133/27415609-ba4b329e-56bc-11e7-9229-57b010a6ddba.png">
