Crash tryng to edit folder description

### ⚠️ Before posting ⚠️

- [x] This is a **bug**, not a question or an enhancement.
- [x] I've [searched for similar issues](https://github.com/nextcloud/android/issues) and didn't find a duplicate.
- [x] I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
- [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/).

### Steps to reproduce

I cannot reprodoce it put I have the report of the application crash, and these were the steps:
- Navigate to the folder
- Open the folder description by tapping on its preview at the top of the screen instead than on the readme.md file (which did not appear at all)
- Once the description is opened, tap on the edit button at the lower let corner
- It doesn't work, tap it some other times at reasonanble distance so that it does not count as double- or triple- taps.

The readme.md file was not visible when entering the folder.

### Expected behaviour

The readme.md file should appear when entering the folder and the description should be editable by opening the preview at the top of the screen and tapping on the edit button at the lower left corner.

### Actual behaviour

The editing page did not open even after tapping several times not so quickly (I did not double-tap, triple-tap or anything: I tappad several times with reasonable pauses between the taps) and then the application showed a crash report.

### Android version

11

### Device brand and model

motorola

### Stock or custom OS?

Stock

### Nextcloud android app version

30320090

### Nextcloud server version

31.0.6

### Using a reverse proxy?

Yes

### Android logs

java
Exception in thread "Thread-41" java.lang.NullPointerException: Attempt to invoke interface method 'com.owncloud.android.ui.helpers.FileOperationsHelper com.owncloud.android.ui.fragment.FileFragment$ContainerActivity.getFileOperationsHelper()' on a null object reference
at com.owncloud.android.ui.preview.PreviewTextStringFragment.lambda$edit$1(PreviewTextStringFragment.java:139)
at com.owncloud.android.ui.preview.PreviewTextStringFragment.$r8$lambda$_MpHYWLzP65yyRQaF66kF_Bz0rY(Unknown Source:0)
at com.owncloud.android.ui.preview.PreviewTextStringFragment$$ExternalSyntheticLambda0.run(D8$$SyntheticClass:0)
at java.lang.Thread.run(Thread.java:923)

### Server error logs

```bash
The crash happened between 6:50 and 6:55

Warning files User Samuele still has unscanned files after running background scan, background scan might be stopper prematurely july 14 2025, 06:55:12
Warning files User Samuele still has unscanned files after running background scan, background scan might be stopper prematurely july 14 2025, 06:55:12
Warning no app in context Capabilities of OCA\CloudFederationAPI/Capabilities took 0.5 seconds to generate july 14 2025,06:53:44
Warning no app in context Capabilities of OCA\CloudFederationAPI/Capabilities took 0.49 seconds to generate july 14 2025,06:53:44
Warning no app in context Capabilities of OCA\CloudFederationAPI/Capabilities took 0.5 seconds to generate july 14 2025,06:53:44
Warning no app in context Capabilities of OCA\CloudFederationAPI/Capabilities took 0.49 seconds to generate july 14 2025,06:53:44
Warning cron Used memory grew mby more than 50 MB when executing job OCA\Passwords\Cron\CheckPasswordsJob (id: 166, arguments: null): 193.8 MB (before: 33 MB) july 14 2025, 06:51:25
Warning cron Used memory grew mby more than 50 MB when executing job OCA\Passwords\Cron\CheckPasswordsJob (id: 166, arguments: null): 193.8 MB (before: 33 MB) july 14 2025, 06:51:25
```

### Additional information

_No response_