App crashes on some devices while adding vaults

### Please agree to the following

- [X] I have searched [existing issues](https://github.com/cryptomator/android/issues?q=) for duplicates
- [X] I agree to follow this project's [Code of Conduct](https://github.com/cryptomator/android/blob/develop/.github/CODE_OF_CONDUCT.md)

### Summary

App crashes on some devices while adding vaults

### System Setup

```markdown
- Android: According to Googe Play Crash logs 7.0 up to 12
- Cryptomator: ?
```

### Cloud Type

_No response_

### Steps to Reproduce

Add a vault, after selecting the `masterkey.cryptomator` or `vault.cryptomator` and resuming Cryptomator, the app crashes. Maybe an error is occurred while listing the root folder but this is just a guess.

### Expected Behavior

App doesn't crash

### Actual Behavior

App crashes

### Reproducibility

Intermittent

### Relevant Log Output

```shell
java.lang.NullPointerException:
at org.cryptomator.presentation.ui.dialog.BaseProgressErrorDialog.showProgress (BaseProgressErrorDialog.kt:47)
at org.cryptomator.presentation.ui.activity.BaseActivity.showProgress (BaseActivity.kt:282)
at org.cryptomator.presentation.workflow.AddExistingVaultWorkflow.cryptomatorFileChosen (AddExistingVaultWorkflow.java:122)
at org.cryptomator.presentation.workflow.SerializableResultCallbacks$2.doCall (SerializableResultCallbacks.java:26)
at org.cryptomator.presentation.workflow.SerializableResultCallbacks$2.doCall (SerializableResultCallbacks.java:24)
at org.cryptomator.generator.BoundCallback.call (BoundCallback.java:33)
at org.cryptomator.presentation.workflow.Workflow.dispatch (Workflow.java:95)
at org.cryptomator.presentation.presenter.Presenter.finishWithResult (Presenter.kt:76)
at org.cryptomator.presentation.presenter.Presenter.finishWithResult (Presenter.kt:62)
at org.cryptomator.presentation.presenter.BrowseFilesPresenter.onFileChosen (BrowseFilesPresenter.kt:759)
at org.cryptomator.presentation.ui.fragment.BrowseFilesFragment$nodeClickListener$1.onFileClicked (BrowseFilesFragment.kt:73)
at org.cryptomator.presentation.ui.adapter.BrowseFilesAdapter$VaultContentViewHolder.bindFile$lambda-3 (BrowseFilesAdapter.kt:192)
at org.cryptomator.presentation.ui.adapter.BrowseFilesAdapter$VaultContentViewHolder.$r8$lambda$KNf3tfJCcvvz5W256_u-x8xov0Y (Unknown Source)
at org.cryptomator.presentation.ui.adapter.BrowseFilesAdapter$VaultContentViewHolder$$ExternalSyntheticLambda1.onClick (Unknown Source:4)
at android.view.View.performClick (View.java:7792)
at android.view.View.performClickInternal (View.java:7769)
at android.view.View.access$3800 (View.java:910)
at android.view.View$PerformClick.run (View.java:30213)
at android.os.Handler.handleCallback (Handler.java:938)
at android.os.Handler.dispatchMessage (Handler.java:99)
at android.os.Looper.loopOnce (Looper.java:226)
at android.os.Looper.loop (Looper.java:313)
at android.app.ActivityThread.main (ActivityThread.java:8663)
at java.lang.reflect.Method.invoke (Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:567)
at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:1135)
```

### Anything else?

_No response_