Git commits in Moodle 2.3.8 by Kyle Temkin

commit 3553982d6d2d7866b13efe20890bb62c2f979925
Author: Kyle Temkin <ktemkin@binghamton.edu>
Date:   Fri, 21 Jun 2013 15:28:59 +0800
Tag:    v2.3.8

MDL-40264 fix essay handling of zero-string response