chakra Inconsistent execution results

###### Version

chakra-1.11.24.0, 1.13.0.0-beta

###### Test case

```js
function foo(){
const b = [{name:"bob",age:25}];
const o = {"__proto__":[[]], "":""};
for (const p in o) {
var a = b[p];
o.__proto__ = {};
}
return JSON.stringify(a)
}
print(foo())
```

###### Execution steps

.ch Testcase.js

###### Output
```
{"name":"bob","age":25}
```

###### Expected result
undefined

###### Description

The correct output of the test case should be `undefined` while chakra yields {"name":"bob","age":25} . I think it might be an issue of chakra.