crash on CSV import screen leads to "broken" postico installation

I helped a colleague recently where a crash in the CSV import screen lead to postico being unusable. I can't give you a full reproduction of the bug, but here is what happened:

- there was a somewhat ambitious CSV import ... maybe the setting (quotes, seperators, etc) where also not correct
- anyway postico crashed with the CSV import settings screen open
- when reopened postico tried to restore the CSV import screen and promptly crashed again
- this lead to a crash loop that I eventually resolved with renaming `~/Library/Containers/at.eggerapps.Postico/Data/Library/Application Support/Postico/Local Library`, restarting postico, quitting and then renaming the library folder back

I wasn't aware before, that postico tries to restore this screen as well ... anyway it can lead to this restart loop if the CSV parser(?) crashes.

Start with the CSV import settings screen and the restoration of that screen from the Postico Local Library path described in the report. Investigate what happens when the CSV parser or import screen crashes during restoration; done means reopening Postico no longer causes a crash loop, including after restarting with the saved import state.

Written by the indexing model from the issue text.