debug string comparing a class

git-svn-id: https://textgridlab.org/svn/textgrid/trunk/middleware/tgauth@9475 7c539038-3410-0410-b1ec-0f2a7bf1c452

info.textgrid.middleware.tgauth.webauth/tglib/RBAC.class.php

@@ -37,7 +37,7 @@ class RBAC {
     $xpath->registerNamespace("c", "http://textgrid.info/namespaces/middleware/tgwebauth");
 
     $this->rbacbase = $xpath->query("/c:conf/c:authz[@instance='${authZinstance}']/c:rbacbase")->item(0)->nodeValue;
-    if ($this->rbacbase->length == 0) {
+    if (!isset ($this->rbacbase) || strlen($this->rbacbase) == 0) {
 	echo "Error: '${authZinstance}' has no RBAC base configured!<br/>\n";
 	return null;
     }