Bad CSS loaded

AKP tries to load a CSS resource inside the wp-admin folder:

<link rel='stylesheet' id='akp-dynamic-css-css' href='http://momsmorningcoffee.com/wp-admin/admin-ajax.php?action=akp_dynamic_css&ver=4.1.1' type='text/css' media='all' />

The content returned (in my case) is just a “0”.

Why AKP loads it? What it does?

https://wordpress.org/plugins/adkingpro/