event reminder email: can't go back if you left out the subject

When adding an event, click on the Event Notifications tab. Enter one notification.

Then, the notification is listed and you have a button to add a second one.

If you add the second one, and fill out all items except leave the subject line blank, you will get an error about the subject line being left blank, and the form will disappear. In my browser, clicking back didn't produce a form with my values.

Since this form provides a way to write what could be a long and thoughtful email, it could lead to frustration for people who lose that work.

Also - the subject field doesn't have an astersisk to indicate that it is required.