The source project of this merge request has been removed.
Enable the allowClear option
Before
After selecting an option from a dropdown list it not possible to clear it. See:
After
An (x) button is added that gives the option to clear:
Technical
To be able to clear an empty option <option value=""></option> must be defined. On the settings part this option is added, on the parameter part it was already there but ignored by forgotten >