datapoints can be added with unchosen day (occasion undefined)

[thermobased]

try:
        cur.execute("""INSERT INTO datapoints (login, habit, occasion, datapoint, comment)
                        VALUES(?, ?, ?, ?, ?)""",
                    (user, new_datapoint_name, new_datapoint_date, new_datapoint_time, new_datapoint))

when new_datapoint_date is not set, Sqlite just eats it as undefined, hence the datapoint never gets rendered anywhere

[thermobased]

fixed by c52bf9169e9389c0e91a1e5804941cad22c277b1