title: Undefined index: HTTP_USER_AGENT in Magento Enterprise 1.10
body: <p>Any ideas why the system.log in magento system is full of this error?</p>
  
  <p>2012-09-04T06:37:25+00:00 ERR (3): Notice: Undefined index: HTTP_USER_AGENT  in /var/www//app/code/core/Mage/Core/Model/Design/Package.php on line 588</p>
  
  <p>we are using Magento Enterprise 1.10, when I was goolging for any hints, seems like it may have something to do with the design theme exception in system->configuration...</p>