N-Triple output broken from empty lang

```
<html
    xmlns="http://www.w3.org/1999/xhtml/"
    xmlns:foaf="http://xmlns.com/foaf/0.1/">
    <head></head>
    <body>
        <p property="foaf:name" xml:lang="">a</p>
    </body>
</html>
```

Ends with "a"@ .
