Update dal.py Table:validate_and_update

Validation has been fixed on validate_and_update method

gluon/dal.py

@@ -9140,7 +9140,7 @@ class Table(object):
                 new_fields[key] = value
 
         if _key is DEFAULT:
-            record = self(**values)
+            record = self(**fields)
         elif isinstance(_key, dict):
             record = self(**_key)
         else: