If `_merge_moves_fields` is called with a recordset of several SM, and if there are more than one `self.picking_id`, the method will trigger a `ValueError` (Expected singleton) OPW-2861605 closes odoo/odoo#100087 X-original-commit: d3924054437cb2add044f51a3c03346a67f24674 Signed-off-by: William Henrotin (whe) <whe@odoo.com> Signed-off-by: Adrien Widart <awt@odoo.com>