Fix bug: MySQL could erroneously return Empty set if InnoDB estimated index range size to 0 records though the range was not empty; MySQL also failed to do the next-key locking in the case of an empty index range


sql/ha_innodb.cc:
  Fix bug: MySQL could erroneously return Empty set if InnoDB estimated index range size to 0 records though the range was not empty; MySQL also failed to do the next-key locking in the case of an empty index range