Prevent crash if MySQL calls rnd_end WITOUT calling rnd_init first: only restore active_index if it the old value was pushed in rnd_init
  Initialize active_index to a sensible value: prevent crash if we restore it to the original value after an table scan


sql/ha_innodb.cc:
  Prevent crash if MySQL calls rnd_end WITOUT calling rnd_init first: only restore active_index if it the old value was pushed in rnd_init