Got this message when loading UCP after installing upgrading to FreePBX 13 and then installing XMPP..(also have firewall enabled)...running on Asterisk 13

Whoops\Exception\ErrorException thrown with message "Class 'Less_Exception_Parser' not found"

Stacktrace:

0 in /var/www/html/admin/modules/ucp/htdocs/includes/less/Cache.php:214

D Rubie