fix crash when getting credentials from keyring

[matrss]

I ran into an issue when trying to connect to mscolab. See:
Screencast from 13.07.2023 14:03:03.webm

This bug was probably introduced in #1731.

This patch catches the exception instead of crashing the app. I am not sure what other side-effects this might have though.

Fixes #1816

[matrss]

After actually testing this on stable and not running into the issue I started a bisect and came to the conclusion that 600d769 introduced the issue, probably due to how it is using get_password_from_keyring. I'll re-target onto develop again, since on stable this issue does not happen.

[matrss]

After further examination it looks like this issue could not have been caught by any test case, since we test against a stub implementation of a keyring backend that does not show this behavior. Maybe this only happens with the gnome keyring I am using, and also works fine on KDE. I cannot test that right now.

Maybe we should just make this function more robust by catching any exception that might occur, since it would be a reasonable default to not provide stored credentials no matter what went wrong trying to get them?

[ReimarBauer]

verified that KDE had not run into this. But we know already that it does it differently. Making it more robust for others is a good point!

Thx