error message on android app after deleting user

### ⚠️ 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 dont know if this is reproducable. I only did this once.

1. create an user profile wfor the same account, but with the IP instead of server name after the @
2. delete the original user profile
3. error message appeared.

### Expected behaviour

I expected to be able to change to change the account details, but that would be a new feature, I guess?

### Actual behaviour

error message

### Android version

Android 15, OneUI 7.0

### Device brand and model

Samsung Tag actice5

### Stock or custom OS?

Stock

### Nextcloud android app version

3.34.0

### Nextcloud server version

31.0.10

### Using a reverse proxy?

No

### Android logs

### Cause of error
```java
Exception in thread "main" java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.String com.nextcloud.client.account.User.getAccountName()' on a null object reference
at com.owncloud.android.ui.activity.FileDisplayActivity.onStart(FileDisplayActivity.kt:2784)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1701)
at android.app.Activity.performStart(Activity.java:9406)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:4492)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:270)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:250)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:232)
at android.app.servertransaction.TransactionExecutor.executeNonLifecycleItem(TransactionExecutor.java:170)
at android.app.servertransaction.TransactionExecutor.executeTransactionItems(TransactionExecutor.java:109)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:81)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2899)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loopOnce(Looper.java:257)
at android.os.Looper.loop(Looper.java:342)
at android.app.ActivityThread.main(ActivityThread.java:9638)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:619)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:929)

```

### App information
* ID: `com.nextcloud.client`
* Version: `30340090`
* Build flavor: `gplay`

### Device information
* Brand: `samsung`
* Device: `gtactive5`
* Model: `SM-X306B`
* Id: `XXXXXXXXXXXXX`
* Product: `gtactive5xeea`

### Firmware
* SDK: `35`
* Release: `15`
* Incremental: `X306BXXS7BYI1`

### Server error logs

```bash
none
```

### Additional information

_No response_