Removed option to send private message if it would go to system. Closes

Closes #4292 

Clicking the message icon was showing user not found. Made it so message icon does not appear if message was generated by system.

![screen shot 2014-11-28 at 7 50 34 pm](https://cloud.githubusercontent.com/assets/2916945/5233224/45e981c8-7738-11e4-9278-fd0c4ac0246f.png)