Use !empty rather than is_array

This picks up the case where the memberof attribute is an empty
array as well as not being an array

modules/ldap/lib/Auth/Process/AttributeAddUsersGroups.php

@@ -263,7 +263,7 @@ class sspmod_ldap_Auth_Process_AttributeAddUsersGroups extends sspmod_ldap_Auth_
             $groups[] = $dn;
 
             // Recursively search "sub" groups
-            if (is_array($attributes[$map['memberof']])) {
+            if (!empty($attributes[$map['memberof']])) {
                 $groups = array_merge($groups, $this->search($attributes[$map['memberof']]));
             }
         }