[ticket/16955] Fix phpdoc annotations and return types

PHPBB3-16955

phpBB/phpbb/auth/provider/base.php

@@ -79,6 +79,7 @@ abstract class base implements provider_interface
 	*/
 	public function login_link_has_necessary_data(array $login_link_data)
 	{
+		return null;
 	}
 
 	/**