Author: Marina Glancy
MDL-58408 completion: can not require grade if grading is not available
Part of MDL-58138 epic
http://git.moodle.org/gw?p=moodle.git;a=commit;h=6445f17bfcfd607f164873b486040ddd89c1a0da
http://github.com/moodle/moodle/commit/6445f17bfcfd607f164873b486040ddd89c1a0da
+ 3.3 en [nogradeitem,core_completion]