[Suggestion] Handle the case of 0.0 points differently when uploading to StudiDB

In the last BuL exam, one student showed up and handed in 0 points. With the current implementation, the student would have appeared to be »nicht erschienen«. As it is not decidable solely based on the total points of 0.0 whether the student actually appeared but failed miserably, or did not even appear, I suggest to not handle this specific case and leave it to manual post-processing. So I would suggest changing this line from

js_string+=f'  "{s.getMartNo()}" : "{grade_data["grade"] if grade_data["sum"] > 0 else "-2.0"}",\n'

to

if grade_data["sum"] > 0:
    js_string+=f'  "{s.getMartNo()}" : "{grade_data["grade"]}",\n'

(and analogously also changing these lines).