KDBX corruption when saving with YubiKey removed

[kylemanna]

As mentioned by @fabian-z

But perhaps the most serious flaw I found is a database corruption, which is triggered when opening a challenge-response secured database, removing the yubikey and then trying to save the database. The save was not delayed as before with no error and apparently led to database corruption (was reproducable for me)! Could you please adress the corruption problem?

keepassx#52 (comment)

Steps to reproduce:

1. Create kdbx with password + yk
2. Add entry / test data and save
3. Remove yk
4. Save kdbx file (will silently fail and encrypt file with garbage)

Possibly other bugs.

Expected behavior:

• Complain to the user that the Yubikey must be re-inserted to save the file or changes will be lost.

[fabian-z]

Confirmed fixed as of b7fd29b 😃

[kylemanna]

This was a big oversight on my part originally. Thanks for catching, reporting, and testing! 🍺