MDL-36167: Assignment quickgrading fix when there is no grade (ensure feedback still saves)
MDL-36167: Assignment quickgrading fix when there is no grade (ensure feedback still saves)

This patch modifies the previous on by Luke Tucker so that the lastmodified hidden field
is always added to the quickgrading form even if there is no grade for the assignment. This
ensures that the lastmodified checks still work (to prevent teachers overwriting each
others feedback) and feedback is saved when there is no grade.

dilawar/moodle