--- a/mailnews/extensions/newsblog/content/FeedItem.js
+++ b/mailnews/extensions/newsblog/content/FeedItem.js
@@ -92,18 +92,19 @@ FeedItem.prototype =
     {
       var ioService = Components.classes["@mozilla.org/network/io-service;1"]
                                 .getService(Components.interfaces.nsIIOService);
       this.mURL = ioService.newURI(aVal, null, null).spec;
     }
     catch(ex)
     {
       // The url as published or constructed can be a non url.  It's used as a
-      // feeditem identifier in feeditems.rdf and as a messageId.  Save as is.
-      this.mURL = aVal;
+      // feeditem identifier in feeditems.rdf, as a messageId, and as an href
+      // and for the content-base header.  Save as is; ensure not null.
+      this.mURL = aVal ? aVal : "";
     }
   },
 
   get date()
   {
     return this.mDate;
   },