Place the following php around the HTML/php code which outputs the media manager button or link:
if(isset($INFO['userinfo'])){ }
For instance, in the new dokuwiki template, you will find the following in tpl_header.php:
<?php
tpl_action('recent', 1, 'li');
tpl_action('media', 1, 'li');
tpl_action('index', 1, 'li');
?>
Change it to:
<?php
global $INFO;
tpl_action('recent', 1, 'li');
if(isset($INFO['userinfo'])){
tpl_action('media', 1, 'li');
}
tpl_action('index', 1, 'li');
?>