Skip check_stock_quantity for sales without warehouse

issue11799
review433611003
(grafted from 3fa390f939c292a7b92f658ea497056f2a3cfdf5)

--HG--
branch : 6.0

sale.py

@@ -66,6 +66,9 @@ class Sale(metaclass=PoolMeta):
         Line = pool.get('sale.line')
         Warning = pool.get('res.user.warning')
 
+        if not self.warehouse:
+            return
+
         transaction = Transaction()
 
         def in_group():