[FIX] stock: empty state

- Update view with external_id=stock.view_move_picking_tree and remove
  editable attribute on the tree view.
- Create a new picking
- Add a line (form view will open) and click on "Save and close"

=> A traceback show up since 'scrapped' was not in the form view.

- The picking location fields become readonly, and the status bar
  disappears
- Save the picking

=> Error: "creation/update: a mandatory field is not correctly set :
   [object with reference: location_id - location.id]"

Courtesy of @benwillig

Closes #17738
opw-748353