WSOD on user/$current_uid/guestbook

i wanted to be able to add guestbooks entries on my own guestbook.

so i themed the guestbook to add "add guestbook entries" also for "own guestbook"

but when the user goes to this page for example user/1/guesbook there is a wsod, because _guestbook_access

<?php
    $form['#access'] = (_guestbook_access('post', $uid) == 'allowed' ? TRUE : FALSE);
?>

returns "own guestbook" here

i'm not sure wether the user should be able to post on their own guestbook by default(adding the link to the theme) but i think it should be at least possible to use it.

attached patch

PS: i think there could be added a variable to enable this, any oppinions about it?