Developer credits
Git commits in Moodle 3.1.3 by Brendan Anderson
commit e50b26fa7ca1c7f0a6c52c6970c9c4f862003ded Author: Brendan Anderson <brendan_anderson@hcpss.org> Date: Tue, 25 Oct 2016 03:22:13 +0800 Tag: v3.1.3 MDL-54112 mod_assign: Add scale null grade filter