Site Slogan not displaying

I've got a sit slogan set for my site (www.couturescoop.com) but it's not appearing in the header as it should.

I've looked at the code and the following bit is evaluating to "true" but nothing is printing out...i'm new to PHP, but i think this means the $site_slogan variable is an empy string. Here's the code:

if (isset($site_slogan)) :

print $site_slogan;

Notably, the slogan appears in the browser's title bar, though I see that comes from a different variable via:

print $head_title

(I don't know where $head_title is set, but somewhere it's picking upt the right value while $site_slogan is not).

Any/all help is appreciated, and feel free to check out the site to see it for yourself.

Thanks!!
--Kris Gonzalez