Empty cloze/IO cards aren't showing in the previewer

### Checked for duplicates?

- [x] This issue is not a duplicate

### Does it also happen in the desktop version?

- [x] This bug does not occur in the latest version of Anki Desktop

### What are the steps to reproduce this bug?

1. Make a cloze/IO note type with 2 distinct deletions/masks.
2. Delete one of them.
3. Open the previewer in the note editor.

Observe that only one card is shown.

Also, the previewer in the template editor shows this weird mix:

### Expected behaviour

All cards are shown like this:

### Debug info

```text
AnkiDroid Version = 2.24.0beta4 (f7293173ab316ff31f72696d9bde126ad1335126)
Backend Version = 0.1.64-anki25.09.2 (25.09.2 3890e12c9e48c028c3f12aa58cb64bd9f8895e30)
Android Version = 13 (SDK 33)
ProductFlavor = full
Device Info = Xiaomi | POCO | mondrian | mondrian_global | 23013PC75G | qcom
WebView Info = [com.google.android.webview | 772705503]: Mozilla/5.0 (Linux; Android 13; 23013PC75G Build/TKQ1.220905.001; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/147.0.7727.55 Mobile Safari/537.36
ACRA UUID = d4397477-c6d7-4d3f-9201-5f836f252781
FSRS = 5.1.0 (Enabled: true)
Crash Reports Enabled = true
```

### (Optional) Anything else you want to share?

_No response_

### Research

- [x] I have checked the [manual](https://ankidroid.org/docs/manual.html) and the [FAQ](https://github.com/ankidroid/Anki-Android/wiki/FAQ) and could not find a solution to my issue
- [x] (Optional) I have confirmed the issue is not resolved in the latest alpha release ([instructions](https://docs.ankidroid.org/manual.html#betaTesting))