The setEmptyString() method on the GroupedDropDownField class doesn't seem to be working.
I have a DropdownField and GroupedDropdownField for testing purposes, calling setEmptyString() on the DropdownField sets the default value as expected, but calling it on the GroupedDropdownField seems to have no effect.
DropdownField::create('Title', 'Title', array('Mr' => 'Mr','Mrs' => 'Mrs'))->setEmptyString('Test');
GroupedDropdownField::create('GroupedDD', 'GroupedDD', array('Group1' => array('Option1' => 'Option1')))->setEmptyString('Test');
Possible bug, or have I made a mistake somewhere?
Thanks