BUG: Update of event fails with no indication

[RodBarnes]

I've found a minor bug that is repeatable:
1. Create a new event.
2. Select "Other facility" and enter some text in "Location".
3. Click [Create Event].
4. Click the event to edit it.
5. Highlight the value in "Location" and cut it (copy and delete).
6. Select "No facility".
7. Click [Update Event].

Nothing happens.

I'm pretty sure this is because, though "Location" is now hidden from view, it was previously marked as invalid. Note that when you cut the value from "Location" it highlights the box. Even though you select "No facility", and hides the box, it is still marked invalid and causes the update to fail but the user is not aware of why it is failing.

Instead, if you just leave the value and click "No facility", it works as expected.