diff --git a/php/classes/UserMgr.php b/php/classes/UserMgr.php
index 5b84185..64108c4 100644
--- a/php/classes/UserMgr.php
+++ b/php/classes/UserMgr.php
@@ -270,7 +270,7 @@ class UserMgr
 					}
 					
 					if ($base->hasAttribute('addable')) {
-					  // keep this base tree 
+					  //   keep this base tree 
 					  //	 error_log($baseId,1,email);
 					}
 					else {
@@ -282,7 +282,13 @@ class UserMgr
 						}
 						else {
 							$center = new $baseId();
-							$centerNode = $center->makeCenterNode($this->paramMgr->xmlDom);
+							if (method_exists($center, 'makeCenterNode'))
+								$centerNode = $center->makeCenterNode($this->paramMgr->xmlDom);
+							else { 
+								// keep this base tree 
+								error_log("Attention : $baseId has no makeCenterNode method", 1, email);
+								continue;
+							}
 							$centerNode->setAttribute('available', TRUE);
 						}
 						
--
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