Author: Andrew Nicols
MDL-67116 course: Fix completion disabled for gradable items
The default value is an empty string (""), which in PHP evaluates to 0 when
cast to a string in our DML layer.
The fix is to forcibly make it null which is not cast to string in DML
for optional strings.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=c0351419714ff44a6fe79561898e7deb784ef365
http://github.com/moodle/moodle/commit/c0351419714ff44a6fe79561898e7deb784ef365
+ 3.8 en [grade_submission_name,mod_workshop]
+ 3.8 en [grade_grading_name,mod_workshop]