[FIX] mrp: traceback when no date_planned_start

Checks the MO `date_planned_start` is set to do the onchange.
Also, add `product_id` in the onchange trigger because the produce delay
can be different for each product and so the MO `date_planned_finished`
must be recomputed also when the product change.

task-2359839

closes odoo/odoo#61295

X-original-commit: b48d0047f6a0a3084739e8991f32aae4a2b399c2
Signed-off-by: William Henrotin <Whenrow@users.noreply.github.com>

addons/mrp/models/mrp_production.py

@@ -567,9 +567,9 @@ class MrpProduction(models.Model):
         self.move_finished_ids = [(2, move.id) for move in self.move_finished_ids]
         self.picking_type_id = self.bom_id.picking_type_id or self.picking_type_id
 
-    @api.onchange('date_planned_start')
+    @api.onchange('date_planned_start', 'product_id')
     def _onchange_date_planned_start(self):
-        if not self.is_planned:
+        if self.date_planned_start and not self.is_planned:
             date_planned_finished = self.date_planned_start + relativedelta(days=self.product_id.produce_delay)
             date_planned_finished = date_planned_finished + relativedelta(days=self.company_id.manufacturing_lead)
             if date_planned_finished == self.date_planned_start: