Prevent text fields with commas being split into multiple elements

I am outputing the body of a node into the dc:description element, but when there are commas in the text (e.g. "Virginia Woolf, “Modern Fiction” from The Common Reader"), it is split into several dc:description elements:

 <dc:description>&lt;p&gt;Virginia Woolf</dc:description>
 <dc:description>“Modern Fiction” from The Common Reader&lt;/p&gt;</dc:description>

The attached patch changes a use of isset() to !empty(), which gives the expected result of:

 <dc:description>&lt;p&gt;Virginia Woolf, “Modern Fiction” from The Common Reader&lt;/p&gt;</dc:description>