Module prints a zero above appended comments

Hello,

I finally got the module working (pretty heavy installation-time) and everything works just fine, but now I got a zero printed between te content and phpbbcomments. (screen attached)

I'm not fancy playing with the .module file self as I'm an adept.

this is how i make my comments work;

in phpbbforum.module:

if (variable_get('phpbbforum_submission_append_to_content_'. $node->type, 0)) {
          if ($vars['phpbbforum_comments']) {
            $phpbbforum_comments_render = '<div id="phpbbforum-node-comments">';
            $phpbbforum_comments_render .= $vars['phpbbforum_comments'];
            $phpbbforum_comments_render .= '</div>';
            $vars['comment'] .= $phpbbforum_comments_render;
            $vars['phpbbforum_comments'] = '';
          }
        }

and this is what I print outside the last div in node.tlp.php
<?php print $comment ?>

It looks pretty easy though, but I just can't relocate where the zere is coming from...

Thanks in advance!