Git commits in Moodle 3.5.2 by Charles Fulton

commit bfc047cef0a623541a5e3a0a7d633c87edd2847b
Author: Charles Fulton <fultonc@lafayette.edu>
Date:   Fri, 29 Jun 2018 00:31:10 +0800
Tag:    v3.5.2

MDL-62534 course formats: do not purge empty sections on upgrade