Error during backup import still results in a broken imported profile

Reported here:
https://support.delta.chat/t/backup-too-new-please-update-delta-chat-message/4761/2

This also previously resulted in users writing instructions for others on how to make a broken setup by ignoring the error:
https://github.com/deltachat/deltachat-android/issues/3871#issuecomment-3170203838

Related previous issue: https://github.com/chatmail/core/issues/4307