Deck deletion causes Default deck to appear in right window when DeckPicker is fragmented

Checked for duplicates?

• This issue is not a duplicate

Does it also happen in the desktop version?

• This bug does not occur in the latest version of Anki Desktop

What are the steps to reproduce this bug?

1. On a tablet or other wide screen, open the DeckPicker.
2. Ensure the collection is non-empty. The screen should be fragmented with the StudyOptionsFragment open on the right.
3. Ensure the Default deck is deleted and not present in the left-hand deck list.
4. Select a deck, then delete it (the collection should still be non-empty).
5. The StudyOptionsFragment displays the Default deck!

https://github.com/user-attachments/assets/3d66a18b-7213-4f6f-939d-864ed7bcf6c6

cc @Haz3-jolt

Expected behaviour

The StudyOptionsFragment should show the next available deck.

Debug info

AnkiDroid Version = 2.24.0 (ebcf8e0e34921628b9b8a496c66ffd4adbb3705f)  Backend Version = 0.1.64-anki25.09.2 (25.09.2 3890e12c9e48c028c3f12aa58cb64bd9f8895e30)  Android Version = 16 (SDK 36)  ProductFlavor = play  Device Info = samsung | samsung | dm1q | dm1qcsx | SM-S911W | qcom  WebView Info = [com.google.android.webview | 772713703]: Mozilla/5.0 (Linux; Android 16; SM-S911W Build/BP2A.250605.031.A3; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/147.0.7727.137 Mobile Safari/537.36  ACRA UUID = 4b66439e-1695-436a-854a-be601b87b058  FSRS = 5.1.0 (Enabled: true)  Crash Reports Enabled = true

(Optional) Anything else you want to share?

No response

Research

• I have checked the manual and the FAQ and could not find a solution to my issue
• (Optional) I have confirmed the issue is not resolved in the latest alpha release (instructions)