Git commits in Moodle 3.1.3 by Eugene Venter

commit 2395ad0dbc57caabe288e07541442ac31723cbf7
Author: Eugene Venter <eugene@catalyst.net.nz>
Date:   Tue, 01 Nov 2016 05:10:21 +0800
Tag:    v3.1.3

MDL-52216 mod_lesson: prevent invalid view modes