In case of 'CREATE VIEW' subselect transformation does not happen(see JOIN::prepare).
During fix_fields Item_row may call is_null() method for its arugmens which
leads to item calculation(wrong subselect in our case as
transformation did not happen before). This is_null() call
does not make sence for 'CREATE VIEW'.
Note:
Only Item_row is affected because other items don't call is_null() 
during fix_fields() for arguments.

mysql-test/r/view.result:
  test case
mysql-test/t/view.test:
  test case
sql/item_row.cc:
  skip is_null() call in case of 'CREATE VIEW' as unnecessary.