Main notes view accessible after signing out / App crash: `NullPointerException` at `getDisplayName()` via `AccountSwitcherDialog`

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Describe the bug
After signing out (profile picture -> „Manage accounts“ -> gear icon -> „Remove“) you can navigate back from the login view using the Android gesture to the Notes list view. The notes are gone but if you click on the profile picture again, the app throws an exception.

To Reproduce

1. Be signed in to a Nextcloud Account
2. Click on your profile picture in the upper-right corner
3. Click on „Manage accounts“
4. Click on the gear icon on the right next to the account
5. Click „Remove“
6. Navigate back using the back android gesture (either the button or the swipe gesture on one of the sides)
7. Click on the profile picture again

Expected behavior
Login view should be an initial view from which you cannot navigate back

Screenshots

N/A

Smartphone (please complete the following information):

• Nextcloud Notes-Version (android app): v3.6.0
• F-Droid or Play Store: F-Droid
• Android-Version: Android 12 (PixelExperience ROM)
• Device: OnePlus 7 (GM1903)

Server

• Nextcloud version: v24.0.5.1 (Nextcloud AIO docker image)
• Nextcloud Notes version (server app): v4.5.1

Stacktrace

App Version: 3.6.0
App Version Code: 3006000
App Flavor: fdroid

Files App Version Code: 30210290

---

OS Version: 4.14.290-ACK-CLO-Hybrid(1660307794)
OS API Level: 32
Device: OnePlus7
Manufacturer: OnePlus
Model (and Product): GM1903 (OnePlus7)

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java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String it.niedermann.owncloud.notes.persistence.entity.Account.getDisplayName()' on a null object reference
	at it.niedermann.owncloud.notes.accountswitcher.AccountSwitcherDialog.lambda$onCreateDialog$3$it-niedermann-owncloud-notes-accountswitcher-AccountSwitcherDialog(AccountSwitcherDialog.java:70)
	at it.niedermann.owncloud.notes.accountswitcher.AccountSwitcherDialog$$ExternalSyntheticLambda4.onChanged(Unknown Source:6)
	at androidx.lifecycle.LiveData.considerNotify(LiveData.java:133)
	at androidx.lifecycle.LiveData.dispatchingValue(LiveData.java:151)
	at androidx.lifecycle.LiveData.setValue(LiveData.java:309)
	at androidx.lifecycle.LiveData$1.run(LiveData.java:93)
	at android.os.Handler.handleCallback(Handler.java:938)
	at android.os.Handler.dispatchMessage(Handler.java:99)
	at android.os.Looper.loopOnce(Looper.java:201)
	at android.os.Looper.loop(Looper.java:288)
	at android.app.ActivityThread.main(ActivityThread.java:7870)
	at java.lang.reflect.Method.invoke(Native Method)
	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1003)

Start with AccountSwitcherDialog.java at line 70 and reproduce the sign-out, back-navigation, and profile-picture flow described in the issue. Inspect how the login view handles Android back navigation and how the account state reaches AccountSwitcherDialog. Done means the login view cannot return to the signed-out notes screen and reopening the profile controls does not crash.