property name updated

Lib/Configuration.php

@@ -53,7 +53,7 @@ class Configuration {
         'www_library_id' => 2,
     );
 
-    private $custom_config = 'configuration.local.php';
+    private $custom_config_filename = 'configuration.local.php';
 
     private function __construct() {
         // by default, set the session save path to the default value;