addon conflict with template: Google Plus One (+1), Facebook Send and Twitter Follow

I have a modified 12leaves.com template and today when i was going to install the > Google Plus One (+1), Facebook Send and Twitter Follow located here

i noticed my )/includes/templates/your_custom_template/common/html_header.php file has an issue with a peice of code from the add on.

<base href="<?php echo (($request_type == 'SSL') ? HTTPS_SERVER . DIR_WS_HTTPS_CATALOG : HTTP_SERVER . DIR_WS_CATALOG ); ?>" />
<?php if (isset($canonicalLink) && $canonicalLink != '') { ?>
<link rel="canonical" href="<?php echo $canonicalLink; ?>" />

<?php if ($this_is_home_page) { ?>
<script src="gxbanner/jquery-1.4.2.js" type="text/javascript"></script>
<script src="gxbanner/gslider.js" type="text/javascript"></script>
<link rel="stylesheet" href="gxbanner/styles_gx.css" type="text/css" />
<?php } ?>

The code in red is in conflict and if i remove one of the red lines i don't get a blank screen but i know that isn't my answer to ths issue.

anyone have any ideas.