(legacy) fix for PHP Warning: Illegal string offset 'radius' in...

(legacy) fix for  PHP Warning:  Illegal string offset 'radius' in /usr/local/www/vpn_l2tp.php on line 37

src/www/vpn_l2tp.php

@@ -34,7 +34,7 @@ require_once("vpn.inc");
 require_once("pfsense-utils.inc");
 require_once("interfaces.inc");
 
-if (!is_array($config['l2tp']['radius'])) {
+if (!isset($config['l2tp']['radius']) || !is_array($config['l2tp']['radius'])) {
     $config['l2tp']['radius'] = array();
 }
 $l2tpcfg = &$config['l2tp'];