Update relation field input value only on demand,
changing the state of a relation_input gadget with value_text = ""
now updates the field.

You can reproduce by doing :
- open an object in tab "View" with a relation field (eg my_successor_title) filled
- open a new tab, and edit the field to make it empty
- from the first tab, refresh the view by click on the left panel "View" tab
- the relation field should be emptied.