Fix possible PHP warning

Aleksander Machniak

2012-05-26 ad8552ea6ffc656fb65480290d00f0572bc1fcd0

 plugins/additional_message_headers/additional_message_headers.php

@@ -19,7 +19,7 @@

    function init()
    {
        $this->add_hook('outgoing_message_headers', array($this, 'message_headers'));
        $this->add_hook('message_outgoing_headers', array($this, 'message_headers'));
    }

    function message_headers($args)