Declare missing property in SimpleSAML\Locale\Language.

lib/SimpleSAML/Locale/Language.php

@@ -57,9 +57,18 @@ class Language
 
     /**
      * HTTP GET language parameter name.
+     *
+     * @var string
      */
     private $languageParameterName;
 
+    /**
+     * A custom function to use in order to determine the language in use.
+     *
+     * @var callable|null
+     */
+    private $customFunction;
+
 
     /**
      * Constructor