Notice: Undefined variable: listtag

The listtag seems supposed to be an attribute for the shortcode, but apparently missing from the code which extracting attributes:

extract(shortcode_atts(array(
		'orderby'		=> 'menu_order ASC, ID ASC',
		'id'			=> $post->ID,
		'itemtag'		=> 'dl',
		'icontag'		=> 'dt',
		'captiontag'	=> 'dd',
		'columns'		=> 3,
		'size'			=> 'thumbnail',
		'include'		=> '',
		'ids'			=> ''
	), $attr));

I commented out the line:
$listtag = tag_escape($listtag);
Now the error message is gone and the plugin works without problems.