Subquery executes twice, at top level JOIN::optimize and ::execute stages.
At first execution create_sort_index() function is called and
FT_SELECT object is created and destroyed. HANDLER::ft_handler is cleaned up
in the object destructor and at second execution FT_SELECT::get_next() method
returns error.
The fix is to reinit HANDLER::ft_handler field before re-execution of subquery.


mysql-test/r/fulltext.result:
  test case
mysql-test/t/fulltext.test:
  test case
sql/item_func.cc:
  reinit ft_handler before re-execution of subquery
sql/item_func.h:
  Fixed method name
sql/sql_select.cc:
  reinit ft_handler before re-execution of subquery