Description:
------------
The code below gives me a segmentation fault when using GtkMessageDialog... I know that I forgot the last parameter (the message), but an error message should shown instead.

Reproduce code:
---------------
<?
$dialog = new GtkMessageDialog(null, Gtk::DIALOG_MODAL, Gtk::MESSAGE_ERROR, Gtk::BUTTONS_OK);
?>

Expected result:
----------------
an error message telling that I forgot the last parameter.

Actual result:
--------------
segmentation fault