Bug #239741 --> Unable to forward messages. regression caused by my earlier checkin to AddAttachment

mail/components/compose/content/MsgComposeCommands.js

@@ -2317,17 +2317,27 @@ function AddAttachment(attachment)
     item.setAttribute("class", "listitem-iconic");
 
     var url = gIOService.newURI(attachment.url, null, null);
-    url = url.QueryInterface( Components.interfaces.nsIURL );
+
+    try 
+    {
+      url = url.QueryInterface( Components.interfaces.nsIURL );
+    }
+    catch (ex)
+    {
+      url = null;
+    }
+
     
     // for local file urls, we are better off using the full file url because moz-icon will
     // actually resolve the file url and get the right icon from the file url. All other urls, we should
     // try to extract the file name from them. This fixes issues were an icon wasn't showing up if you dragged
     // a web url that had a query or reference string after the file name and for mailnews urls were the filename
     // is hidden in the url as a &filename= part.
-    if (url.fileName && !url.schemeIs("file")) 
+    if (url && url.fileName && !url.schemeIs("file")) 
       item.setAttribute("image", "moz-icon://" + url.fileName);
     else      
       item.setAttribute("image", "moz-icon:" + attachment.url);
+    
     bucket.appendChild(item);
   }
 }