[FIX] sale: copy of possibly None context

closes #10488

addons/sale/sale.py

@@ -313,7 +313,9 @@ class sale_order(osv.osv):
         return {'warning': warning, 'value': value}
 
     def get_salenote(self, cr, uid, ids, partner_id, context=None):
-        context_lang = context.copy() 
+        if context is None:
+            context = {}
+        context_lang = context.copy()
         if partner_id:
             partner_lang = self.pool.get('res.partner').browse(cr, uid, partner_id, context=context).lang
             context_lang.update({'lang': partner_lang})