meta keywords in template.php should contain HTML-escaped strings

After validating my personal web site with the W3C validator, the latter kept complaining about not valid tags inside the meta description tag inside the page header. Looking at the source, the page returned:

<meta name="description" content="<p>site slogan</p>" />

Obviously, the site slogan must not contain any unescaped HTML tags inside the content attribute. A quick and dirty solution is to change line 151 of template.php:

$keywords = '<meta name="description" content="'. theme_get_setting('meta_description') .'" />';

with

$keywords = '<meta name="description" content="'. $slogan .'" />';