[FIX] mrp: do not rename warehouse when changing code

If only the code of a warehouse is changed, `name` is None.
Do not try to set None as the new pull name.

Fixes #14766

addons/mrp/models/stock_warehouse.py

@@ -122,6 +122,6 @@ class StockWarehouse(models.Model):
         res = super(StockWarehouse, self)._update_name_and_code(name, code)
         # change the manufacture procurement rule name
         for warehouse in self:
-            if warehouse.manufacture_pull_id:
+            if warehouse.manufacture_pull_id and name:
                 warehouse.manufacture_pull_id.write({'name': warehouse.manufacture_pull_id.name.replace(warehouse.name, name, 1)})
         return res