Can't change vault "Unlock Duration" while unlocked

### Please agree to the following

- [X] I have searched [existing issues](https://github.com/cryptomator/ios/issues?q=) for duplicates
- [X] I agree to follow this project's [Code of Conduct](https://github.com/cryptomator/ios/blob/develop/.github/CODE_OF_CONDUCT.md)

### Summary

Can't change vault "Unlock Duration" while unlocked

### System Setup

- iOS: 15.3.1
- Cryptomator: 2.1.2 (838)

### Cloud Type

_No response_

### Steps to Reproduce

1. Tap on unlocked vault
2. Tap on Unlock Duration
3. Tap on "Indefinite"
4. Tap on "Confirm & Lock Now"

### Expected Behavior

It should lock the vault, and change the unlock duration.

### Actual Behavior

It gives me an error message (see screenshot below). Note that this has worked in the past, but now it doesn't, and it repeatedly doesn't. Manually locking and changing the duration works, though.

### Reproducibility

Intermittent

### Relevant Log Output

_No response_

### Anything else?


Start by reproducing the listed steps on the iOS setup described, then compare the failing “Confirm & Lock Now” flow with manually locking and changing the duration. The issue is done when changing Unlock Duration from an unlocked vault reliably locks the vault and applies the selected duration without the reported error.

Written by the indexing model from the issue text.