I have set up a pretty conventional workshop. It progressed in to Assessment phase. Once a participant tries to assess another, Moodle throws "Undefined variable: type in moodle/lib/pear/HTML/QuickForm/group.php on line 277" Interestingly three times - for the three missing boxes(?). See screen-shots.
Moodle 2.7.19 (Build: 20170313)
LAMP, PHP Version 5.6.30-0+deb8u1, MySQL 5.5.54
(The same installation as in "Creating a new wiki throws error/moodle/invalidcoursemodule" https://moodle.org/mod/forum/discuss.php?d=350178. Yes, I cleared the caches!)