The problem is that during temporary table creation uneven bits
are not taken into account for hidden fields. It leads to incorrect
calculation&allocation of null bytes size for table record. And
if grouped value is null we set wrong bit for this value(see end_update()).
Fixed by adding separate calculation of uneven bit for hidden fields.


mysql-test/r/type_bit.result:
  test case
mysql-test/t/type_bit.test:
  test case
sql/sql_select.cc:
  added separate calculation of uneven bit for hidden fields