Issues opening Nextcloud after adding 2-way sync

### ⚠️ 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

### Cause of error
```java
Exception in thread "Syncfolder thread" java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String com.owncloud.android.datamodel.OCFile.getEtag()' on a null object reference
at com.owncloud.android.operations.SynchronizeFolderOperation.checkForChanges(SynchronizeFolderOperation.java:172)
at com.owncloud.android.operations.SynchronizeFolderOperation.run(SynchronizeFolderOperation.java:131)
at com.owncloud.android.lib.common.operations.RemoteOperation.execute(RemoteOperation.java:193)
at com.owncloud.android.services.SyncFolderHandler.doOperation(SyncFolderHandler.java:106)
at com.owncloud.android.services.SyncFolderHandler.handleMessage(SyncFolderHandler.java:79)
at android.os.Handler.dispatchMessage(Handler.java:112)
at android.os.Looper.loopOnce(Looper.java:268)
at android.os.Looper.loop(Looper.java:384)
at android.os.HandlerThread.run(HandlerThread.java:103)

```

### App information
* ID: `com.nextcloud.client`
* Version: `30310490`
* Build flavor: `gplay`

### Device information
* Brand: `motorola`
* Device: `vienna`
* Model: `motorola edge 50 neo`
* Id: `V1UI35H.11-39-16`
* Product: `vienna_g_syses`

### Firmware
* SDK: `35`
* Release: `15`
* Incremental: `759d6a-588dde`

### Expected behaviour

I should be able to open Nextcloud on my android phone.

### Actual behaviour

Getting this stacktrace after opening Nextcloud on my phone.

### Android version

15

### Device brand and model

Motorola edge 50 neo

### Stock or custom OS?

Stock

### Nextcloud android app version

not able to open nextcloud app

### Nextcloud server version

30.0.6

### Using a reverse proxy?

Yes

### Android logs

_No response_

### Server error logs

```bash

```

### Additional information

_No response_