[FIX] stock: calling 'get()' on None

This commit tests that values is not falsy before accessing a key

closes odoo/odoo#34343

Signed-off-by: Simon Lejeune (sle) <sle@openerp.com>

addons/stock/models/stock_warehouse.py

@@ -679,7 +679,7 @@ class Warehouse(models.Model):
             route_rule_values.update(values or {})
             rules_list.append(route_rule_values)
             first_rule = False
-        if values.get('propagate_cancel') and rules_list:
+        if values and values.get('propagate_cancel') and rules_list:
             # In case of rules chain with cancel propagation set, we need to stop
             # the cancellation for the last step in order to avoid cancelling
             # any other move after the chain.