Fixing PR error

As checked via Triple:

```
> _isObject({}.__proto__);
true
> _isObject(Ti.UI.createWindow().__proto__);
false
> _isObject(Ti.UI.create2DMatrix().__proto__);
false
> _isObject([].__proto__);
true
> _isObject(''.__proto__);
true
```

versus:

```
> _isObject({}.__prototype);
false
```