Event with invalid date is persisted to the database

[inakijaneiro]

If you create an event in an invalid date (let's say, december 34th, 2019). An error is thrown, however, the event is still persisted in the database and can be accesed from the "Parties im throwing" section.

[inakijaneiro]

#19 Fixes empty fields breaking the database. Users can still enter an invalid date, however, it is now more clear how the data format is expected.