Git commits in Moodle 3.5.1 by sam marshall

commit c843630aee89f510b5559c8e7769d011dc4eaa2b
Author: sam marshall <s.marshall@open.ac.uk>
Date:   Fri, 29 Jun 2018 17:48:16 +0800
Tag:    v3.5.1

MDL-62713 core_search: Cron error indexing sections in some cases