Problems with restoring backups

### Checked for duplicates?

- [x] 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?

These are three related bugs in one issue. I can split them if necessary.

**A) Broken backup files:**

I don't know how to reproduce this bug. I haven't touched the backups ever (probably). I have probably created some backups manually to test the new 2.24 "Create backup" feature, but I doubt these specific backups were manually created.

The error on the right is caused by the 15:38 file which is empty (0 bytes). Again, I didn't make these files nor modified them.

**B) No search button and sync warning icon:**

I can reproduce this one by first attempting to restore the 16:33 backup which shows the error on the left (see above), then switching to another app and back twice.

https://github.com/user-attachments/assets/52ad54a6-a0f9-49d8-8016-398a5cf30ca8

**C) This is minor, but you can see in the recording that pressing cancel returns to the first dialog.**

### Expected behaviour

- Every backup should work.
- The search icon and sync warning shouldn't disappear.
- Pressing cancel on the backup selection dialog should not show the previous dialog.

### Debug info

```text
AnkiDroid Version = 2.24.0 (ebcf8e0e34921628b9b8a496c66ffd4adbb3705f)
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 | 777812003]: Mozilla/5.0 (Linux; Android 13; 23013PC75G Build/TKQ1.220905.001; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/148.0.7778.120 Mobile Safari/537.36
ACRA UUID = 4afc3b3f-e93f-4a66-bc71-2b9476ef9eb0
FSRS = 5.1.0 (Enabled: true)
Crash Reports Enabled = true
```

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

Nitpick: there's no snackbar confirming that the restoration was successful.

### 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))