fixed small bug

git-svn-id: http://framework.zend.com/svn/framework/standard/trunk@18893 44c647ce-9c0f-0410-b52a-842ac1e357ba

library/Zend/Ldap.php

@@ -948,7 +948,7 @@ class Zend_Ldap
         }
         if (!is_null($sort) && is_string($sort)) {
             $isSorted = @ldap_sort($this->getResource(), $search, $sort);
-            if($search === false) {
+            if($isSorted === false) {
                 /**
                  * @see Zend_Ldap_Exception
                  */