Cannot fill in field for guest registration

One-sentence description

It is not possible to enter data in a event registration field

Current behaviour / Reproducing the bug

1. Go to event
2. Click on a guest registration (I did not try what happens if I try to change this field for a member registration)
3. Click 'edit registration field'
4. Enter the data
5. Hit enter (as there is no save button). 5a. get the banner 'data has been saved'
6. Close the registration
7. Go to the event
8. Data is not saved, the registration field is still emty :(

Expected behaviour

Data can be added to the registration fields