[fix][#30181] Error in joomla content plugin if no one is assigned to get email

Updated patch for https://github.com/joomla/joomla-cms/pull/764 and issue tracker:
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=30181

![die-article](https://cloud.githubusercontent.com/assets/1119272/3252786/2c625eaa-f1c8-11e3-9c5d-01d154540ac4.png)