[FIX] stock: Use current datetime when no Scheduled date

Same as the default get
This field should probably be set as required in master

Fixes #29778

closes odoo/odoo#29781

addons/stock/wizard/product_replenish.py

@@ -72,7 +72,7 @@ class ProductReplenish(models.TransientModel):
         values = {
             'warehouse_id': self.warehouse_id,
             'route_ids': self.route_ids,
-            'date_planned': self.date_planned,
+            'date_planned': self.date_planned or fields.Datetime.now(),
             'group_id': replenishment,
         }
         return values