Git commits in Moodle 3.1.4 by Tobias Reischmann

commit 25bb8b64f95d6bd339b87eed7cc6e9df4dbb38cc
Author: Tobias Reischmann <tobias.reischmann@wi.uni-muenster.de>
Date:   Wed, 16 Nov 2016 23:49:16 +0800
Tag:    v3.1.4

MDL-55275 assign: Prevent exception under admin role assignment.