datatype rdf:HTML not properly handled #13

From @darobin on March 11, 2016 14:44

This is similar to #16. The following code actually trips over and errors in the console:

<span vocab="http://schema.org/" typeof="Document">
  <span property="dc:title" datatype="rdf:HTML">RDFa <b>1.1</b> Primer</span>
</span>

What's going on is that the value is actually a DOM node. It tries to figure out what to do with it by looking at its type; but of course the DOM node doesn't have one. So it tries to escape it as a string, which simply doesn't work.

Copied from original issue: rdfa/rdfa-website#52