[FIX] sale_mrp: allow production without finished products

Have a mrp.production that you cancel, and delete the finished products lines

Before this commit, the computation of the sale_name crashed because we did
an index selection on an empty recordset

After this commit, there is no crash

opw 1851217
closes #24923

addons/sale_mrp/sale_mrp.py

@@ -18,7 +18,7 @@ class MrpProduction(models.Model):
                 return get_parent_move(move.move_dest_id)
             return move
         for production in self:
-            move = get_parent_move(production.move_finished_ids[0])
+            move = get_parent_move(production.move_finished_ids[:1])
             production.sale_name = move.procurement_id and move.procurement_id.sale_line_id and move.procurement_id.sale_line_id.order_id.name or False
             production.sale_ref = move.procurement_id and move.procurement_id.sale_line_id and move.procurement_id.sale_line_id.order_id.client_order_ref or False