App crashes on Pixel 7 sharing files with nextcloud server

### ⚠️ 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. Select a file (PDF) with Android file broswer
2. Select "share with" (German: teilen) and then "Nextcloud"
3. confirm
4. Upload crashes with NullPointer Exception

see section "Android logs"

### Expected behaviour

Upload a file from mobile phone to my Nextcloud server

### Actual behaviour

Don't upload because of a crash

### Android version

15

### Device brand and model

Google Pixel 7 Pro

### Stock or custom OS?

Stock

### Nextcloud android app version

330010090

### Nextcloud server version

33.0.2

### Using a reverse proxy?

No

### Android logs

Exception in thread "main" java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.Set com.owncloud.android.ui.adapter.ReceiveExternalFilesAdapter.getFileNames()' on a null object reference
at com.owncloud.android.ui.activity.ReceiveExternalFilesActivity.lambda$getFileNameTextWatcher$6(ReceiveExternalFilesActivity.java:907)
at com.owncloud.android.ui.activity.ReceiveExternalFilesActivity.$r8$lambda$7aQSDlHWZ2ECuUzMqE_fcn8_TAk(Unknown Source:0)
at com.owncloud.android.ui.activity.ReceiveExternalFilesActivity$$ExternalSyntheticLambda11.invoke(D8$$SyntheticClass:0)
at com.nextcloud.utils.fileNameValidator.FileNameTextWatcher.afterTextChanged(FileNameTextWatcher.kt:43)
at android.widget.TextView.sendAfterTextChanged(TextView.java:12934)
at android.widget.TextView.setText(TextView.java:7550)
at android.widget.TextView.setText(TextView.java:7348)
at android.widget.EditText.setText(EditText.java:184)
at android.widget.TextView.setText(TextView.java:7286)
at com.owncloud.android.ui.activity.ReceiveExternalFilesActivity.setupFileNameInputField(ReceiveExternalFilesActivity.java:875)
at com.owncloud.android.ui.activity.ReceiveExternalFilesActivity.populateDirectoryList(ReceiveExternalFilesActivity.java:803)
at com.owncloud.android.ui.activity.ReceiveExternalFilesActivity.browseToFolderIfItExists(ReceiveExternalFilesActivity.java:274)
at com.owncloud.android.ui.activity.ReceiveExternalFilesActivity.onStart(ReceiveExternalFilesActivity.java:266)
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1718)
at android.app.Activity.performStart(Activity.java:9333)
at android.app.ActivityThread.handleStartActivity(ActivityThread.java:4545)
at android.app.servertransaction.TransactionExecutor.performLifecycleSequence(TransactionExecutor.java:214)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:194)
at android.app.servertransaction.TransactionExecutor.cycleToPath(TransactionExecutor.java:176)
at android.app.servertransaction.TransactionExecutor.executeNonLifecycleItem(TransactionExecutor.java:129)
at android.app.servertransaction.TransactionExecutor.executeTransactionItems(TransactionExecutor.java:103)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:80)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2987)
at android.os.Handler.dispatchMessageImpl(Handler.java:142)
at android.os.Handler.dispatchMessage(Handler.java:125)
at android.os.Looper.loopOnce(Looper.java:269)
at android.os.Looper.loop(Looper.java:367)
at android.app.ActivityThread.main(ActivityThread.java:9333)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:566)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:929)
App information
ID: com.nextcloud.client
Version: 330010090
Build flavor: gplay
Device information
Brand: google
Device: cheetah
Model: Pixel 7 Pro
Id: CP1A.260405.005
Product: cheetah
Firmware
SDK: 36
Release: 16
Incremental: 15001963

### Server error logs

```bash

```

### Additional information

_No response_