EllisLab/CodeIgniter — pull request #2597 by timwis (2013-08-11 02:23:21+00:00)
Title: Fixed validation bug that treated "not set" and "set but empty string" the same

Fixed validation bug that treated "not set" and "set but empty string" the same

See forum thread for more details http://ellislab.com/forums/viewthread/237094/