Empty folders „_Contacts-Backup“ and „_Calendar-Backup“ are created during calendar and contacts Backup

### ⚠️ 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

1.) Enable Backup of calendar and contacts
2.) Run a Backup

### Expected behaviour

Folders should Not be created.

### Actual behaviour

The calendar and contacts backup files are correctly stored in the corresponding folder „.Contacts-Backup“ and „.Calendar-Backup“, but the folders mentioned above are created if it‘s not existing.

### Android version

14

### Device brand and model

Samsung Galaxy A52

### Stock or custom OS?

Stock

### Nextcloud android app version

3.31.1

### Nextcloud server version

31.0.3.2

### Using a reverse proxy?

No

### Android logs

_No response_

### Server error logs

```bash

```

### Additional information

Here is an excerpt of the oc_activity table

from_unixtime(TIMESTAMP);activity_id;subject;subjectparams;FILE
2025-04-17 13:20:46;197808;deleted_self;[{"499943":"\/_Contacts-Backup"}];/_Contacts-Backup
2025-04-17 13:48:59;197809;created_self;[{"499973":"\/_Calendar-Backup"}];/_Calendar-Backup
2025-04-17 13:49:01;197810;created_self;[{"499974":"\/.Calendar-Backup\/My calendar_2025-04-17_13-48-57.ics"}];/.Calendar-Backup/My calendar_2025-04-17_13-48-57.ics
2025-04-17 13:49:02;197811;created_self;[{"499975":"\/.Calendar-Backup\/Feiertage in Deutschland_2025-04-17_13-48-58.ics"}];/.Calendar-Backup/Feiertage in Deutschland_2025-04-17_13-48-58.ics
2025-04-17 13:49:07;197812;created_self;[{"499976":"\/.Calendar-Backup\/Pers\u00f6nlich_2025-04-17_13-48-59.ics"}];/.Calendar-Backup/Persönlich_2025-04-17_13-48-59.ics
2025-04-17 13:49:08;197813;created_self;[{"499977":"\/.Calendar-Backup\/Wichtige Daten der Kontakte_2025-04-17_13-49-06.ics"}];/.Calendar-Backup/Wichtige Daten der Kontakte_2025-04-17_13-49-06.ics
2025-04-17 13:49:23;197814;created_self;[{"499978":"\/_Contacts-Backup"}];/_Contacts-Backup
2025-04-17 13:49:24;197815;created_self;[{"499979":"\/.Contacts-Backup\/2025-04-17_13-49-22.vcf"}];/.Contacts-Backup/2025-04-17_13-49-22.vcf