Edit_event: 0 indexes given does not throw error

[nus-pe-bot]

Edit date
edit_event --end "19/11/2019 00:00"
Should not be a valid command. The toast at the top screen shows “Events edited: “
Even though it should not be a valid command as an index is not provided

edit_event 0 --end "19/11/2019 00:00"
Should not be a valid command. The event’s end date is still before the event’s start date. And should not be allowed to edit the task’s end date to be before the start date.

edit_event 0 --remind "18/11/2019 00:00"
Should not be a valid command. Reminder should not be after the event’s add date.

doesn't make sense for end date to before start date
and reminder date to be after everything

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_{[original: kwekke/ped#2]}

[ghost]

Issue with edit_event: No indexes should throw CommandException
Issue with EventSource: Should not allow creation of events with end/remind date before start date.

[ghost]

Fixed in #211, closing.