Bug 375215 - FeedWriter fails for feeds with text/html content type

p=Wladimir Palant <trev@gtchat.de>r=sayrer/mano

browser/components/feeds/src/FeedWriter.js

@@ -340,7 +340,8 @@ FeedWriter.prototype = {
         else
           LOG("no base?");
         docFragment = summary.createDocumentFragment(body);
-        body.appendChild(docFragment);
+        if (docFragment)
+          body.appendChild(docFragment);
 
         // If the entry doesn't have a title, append a # permalink
         // See http://scripting.com/rss.xml for an example