Field settings "Select Style" always shows "Blue" skin if we want to use "No Styling"

Steps to reproduce:

1. Open /admin/structure/types/manage/event/fields/node.event.field_add_to_calendar
2. Choose "No Styling" and save the field
3. Open field's setting again and you will see "Blue" by default

It isn't critical if the site uses "Blue" or "Orange" skins, however, is critical when a developer uses own CSS styles and edited the field forgetting to choose "No Styling", in this case, the theming for the widget can be broken because the site has additional CSS.