fix(filename text watcher): existing file names provider npe

[alperozturk96]

Issue

Exception java.lang.NullPointerException:
  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)
  at com.owncloud.android.ui.activity.ReceiveExternalFilesActivity$$ExternalSyntheticLambda11.invoke (D8$$SyntheticClass)
  at com.nextcloud.utils.fileNameValidator.FileNameTextWatcher.afterTextChanged (FileNameTextWatcher.kt:43)
  at android.widget.TextView.sendAfterTextChanged (TextView.java:13603)
  at android.widget.TextView.setText (TextView.java:7949)
  at android.widget.TextView.setText (TextView.java:7719)
  at android.widget.EditText.setText (EditText.java:184)
  at android.widget.TextView.setText (TextView.java:7657)
  at android.widget.TextView.onRestoreInstanceState (TextView.java:7524)
  at android.view.View.dispatchRestoreInstanceState (View.java:24610)
  at android.view.ViewGroup.dispatchRestoreInstanceState (ViewGroup.java:4279)
  at android.view.ViewGroup.dispatchRestoreInstanceState (ViewGroup.java:4279)
  at com.google.android.material.textfield.TextInputLayout.dispatchRestoreInstanceState (TextInputLayout.java:3208)
  at android.view.ViewGroup.dispatchRestoreInstanceState (ViewGroup.java:4279)
  at android.view.ViewGroup.dispatchRestoreInstanceState (ViewGroup.java:4279)
  at android.view.ViewGroup.dispatchRestoreInstanceState (ViewGroup.java:4279)
  at android.view.ViewGroup.dispatchRestoreInstanceState (ViewGroup.java:4279)
  at android.view.View.restoreHierarchyState (View.java:24588)
  at com.android.internal.policy.PhoneWindow.restoreHierarchyState (PhoneWindow.java:2435)
  at android.app.Activity.onRestoreInstanceState (Activity.java:2056)
  at com.owncloud.android.ui.activity.DrawerActivity.onRestoreInstanceState (DrawerActivity.java:1163)
  at android.app.Activity.performRestoreInstanceState (Activity.java:2009)
  at android.app.Instrumentation.callActivityOnRestoreInstanceState (Instrumentation.java:1571)
  at android.app.ActivityThread.handleStartActivity (ActivityThread.java:4770)
  at android.app.servertransaction.TransactionExecutor.performLifecycleSequence (TransactionExecutor.java:214)
  at android.app.servertransaction.TransactionExecutor.cycleToPath (TransactionExecutor.java:194)
  at android.app.servertransaction.TransactionExecutor.executeLifecycleItem (TransactionExecutor.java:166)
  at android.app.servertransaction.TransactionExecutor.executeTransactionItems (TransactionExecutor.java:101)
  at android.app.servertransaction.TransactionExecutor.execute (TransactionExecutor.java:80)
  at android.app.ActivityThread$H.handleMessage (ActivityThread.java:3150)
  at android.os.Handler.dispatchMessage (Handler.java:110)
  at android.os.Looper.loopOnce (Looper.java:273)
  at android.os.Looper.loop (Looper.java:363)
  at android.app.ActivityThread.main (ActivityThread.java:10060)
  at java.lang.reflect.Method.invoke
  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:632)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:975)

Changes

Makes existingFileNamesProvider non-nullable.

[github-actions]

Codacy

SpotBugs

Category	Base	New
Bad practice	35	35
Correctness	67	71
Dodgy code	219	221
Experimental	1	1
Internationalization	7	7
Malicious code vulnerability	2	2
Multithreaded correctness	34	34
Performance	42	42
Security	16	16
Total	423	429

SpotBugs increased!

[github-actions]

APK file: https://github.com/nextcloud/android/actions/runs/25047417845/artifacts/6681833618
To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.
(please click on link to get QR code displayed)

[github-actions]

blue-Light-Screenshot test failed, but no output was generated. Maybe a preliminary stage failed.

[alperozturk96]

/backport to stable-33.1.x