info.magnolia.ui.field.factory.FieldBinder.Default uses method com.vaadin.data.Binder.BindingBuilder#withNullRepresentation to propagate default value from field definition. This cause that field can't be set to empty because then it's every time converted to default value

On the other hand info.magnolia.ui.field.TextFieldBinder set com.vaadin.data.Binder.BindingBuilder#withNullRepresentation to empty string which cause that default values is never used

Reproduce:
Issue 1

        select:
          label: select
          $type: comboBoxField
          emptySelectionAllowed: true
          defaultValue: Bartok
          datasource:
            $type: optionListDatasource
            options:
              - name: Vivaldi
                value: Vivaldi
              - name: Bach
                value: Bach
              - name: Bartok
                value: Bartok

This definition allows empty selection in combobox, but after selecting the empty option and reopening dialog "Bartok" (defaultValue) is selected instead of the empty one

Issue 2

        salutation:
          label: salutation
          $type: textField
          defaultValue: Mr
          description: hello

In this definition defaultValue is completely ignored, because TextFieldBinder instead sets empty string