Fix missing depends and manage None as value of field in on_change method

issue6069
review27851002

sale.py

@@ -56,7 +56,9 @@ class Sale:
 
     def _get_carrier_selection_pattern(self):
         pattern = {}
-        if self.warehouse.address and self.warehouse.address.country:
+        if (self.warehouse
+                and self.warehouse.address
+                and self.warehouse.address.country):
             pattern['from_country'] = self.warehouse.address.country.id
         if self.shipment_address and self.shipment_address.country:
             pattern['to_country'] = self.shipment_address.country.id

stock.py

@@ -43,7 +43,7 @@ class ShipmentOut:
                     'product "%s".'),
                 })
 
-    @fields.depends('currency')
+    @fields.depends('cost_currency')
     def on_change_with_cost_currency_digits(self, name=None):
         if self.cost_currency:
             return self.cost_currency.digits