I'm having the same crashing problem on my iPad with iOS 9.3.5 since the update on 28th December.
I see here that the issue has been acknowledged but please fix with an update urgently or revert to version 5.
I agree that the app should not have updated if it is not compatible with the older iOS devices. Compatability with my older iPad was a key selling point for me to buy this password app. It worked so well until this update.