Once set, one cannot remove some metadata in the create event dialog
Steps to reproduce
Go to the create new event dialog
Click on edit language (example)
Decide you do not want to set a language
Try to get rid of the language field
The list of values passed to the selection doesn't have a empty value (because "" can't be a key), however the default value is set to "". When angularJS sees a value that is not in the list it creates the empty option as it doesn't want to select one for you. Once you've selected a value the empty option is removed.
So we need to add a valid blank option, either by putting it in the html or adding it to the array of values (again hard as this appears to be key: value map)