Git commits in Moodle 3.8.4 by Marina Glancy

commit d690ed3dd3ad6c511354b6ccf20261200d237ebf
Author: Marina Glancy <marina@moodle.com>
Date:   Tue, 23 Jun 2020 22:02:33 +0800
Tag:    v3.8.4

MDL-69109 theme: try to load icons from the current theme


commit 704153c45461cb1d2caa35c0d84258b461d25637
Author: Marina Glancy <marina@moodle.com>
Date:   Mon, 22 Jun 2020 21:09:15 +0800
Tag:    v3.8.4

MDL-69109 core: use different cache keys for FA icon maps


commit aecc9e717092b1a90b3e4fcba6b7b4e7cfaffe69
Author: Marina Glancy <marina@moodle.com>
Date:   Wed, 04 Mar 2020 02:55:52 +0800
Tag:    v3.8.4

MDL-68099 gradereport_grader: prevent exception without groups