Summary:
no values assigned to $seo_keywords, $title_keywords, $default_keywords, $page_keywords
Detailed Description:
If you try to use the smarty vars for above mentioned values you won't get any
output.
further investigations pointed out, that $smarty->assign('NAME','VALUE') will
not work as expected in action.default.php and no values will be assigned. Also
the vars won't be recognized by smarty subsystem (f.e. if you use the smarty
function {debug} they won't show up).