ComboBox with empty value

Hi! I need in Vaadin 24 that a ComboBox shows me at the top of the object list an empty value. For instance, if the list has three elements I need the ComboBox shows me an empty value at the top in case that the user doesn’t want to select anything. I used to do that in Vaadin 8 but I can’t find to do it here.
ComboBox.png

https://vaadin.com/docs/latest/components/combo-box#custom-value-entry