problem with  {attr: false}

If i set 
```
{
attr: false
}
```
as in documentation, it become default 
```

  "attr": {
    "list": [
      "data-i18n"
    ],
    "extensions": [
      ".html",
      ".htm"
    ]
  },

```
this behaviour is repeated if i set it to `undefined` or `null`
