Added removal of _cached_index attribute on rollback to Index class.!
Added removal of _cached_index attribute on rollback to Index class.!

quantifiedcode-bot/blitzdb,cwoebker/blitzdb,ghislainp/blitzdb,adewes/blitzdb,programmdesign/blitzdb,programmdesign/blitzdb,kylewm/blitzdb,programmdesign/blitzdb,orgkhnargh/blitzdb