Dwoo support: fixing friends page, and display_name value checking

htdocs/lib/dwoo/mahara/plugins/function.display_name.php

@@ -10,7 +10,7 @@
  * @version  1.0
  */
 function Dwoo_Plugin_display_name(Dwoo $dwoo, $user) {
-    if (!is_object($user)) {
+    if (!$user) {
         return '';
     }
 

htdocs/theme/raw/templates/user/user.tpl

@@ -60,7 +60,7 @@
 	<div class="rightdiv">
 	<h3>
 		<a href="{$WWWROOT}user/view.php?id={$user->id}">
-			{$user->id|display_name|escape}
+			{$user|display_name|escape}
 		</a>
 		{if $page == 'find'}
 			- {str tag='existingfriend' section='group'}