As a student (testing user) I submitted a file so teachers can confirm rubric and marking in the live setting.
Once completed I want to remove the test student submission so it does not get mixed with the real ones.
So set submission back to braft.
Login as student, edit submission, delete file.
Now prevented from saving changes (removing file) as Error is returned "Nothing was submitted"
Needs to Save anyway. If there are no files and Moodle saves 'No files' what does that matter?