Invalid sync server specified. Please check the preferences.

### 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?

I installed Anki 25.07.3, configured it, created decks, synced it with AnkiWeb, installed AnkiDroid 2.21.1, gave it all permisions, loged in to AnkiWeb, and typed the sync button at the top right corner


### Expected behaviour

The notification above shouldn't appear at all

### Debug info

```text
AnkiDroid Version = 2.21.1 (5dcdec8a8891153d8480a8ece2cdc44327cb2ff9)
Backend Version = 0.1.54-anki25.02.7 (25.02.7 98253c81cb3c4d203acec48d6eae6b488bf484d0)
Android Version = 15 (SDK 35)
ProductFlavor = play
Device Info = Xiaomi | POCO | duchamp | duchamp_global | 2311DRK48G | mt6897
Webview User Agent = Mozilla/5.0 (Linux; Android 15; 2311DRK48G Build/AP3A.240905.015.A2; wv) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/138.0.7204.157 Mobile Safari/537.36
ACRA UUID = dd827a30-fe34-457a-98fb-9205c4715613
FSRS = 2.0.3 (Enabled: true)
Crash Reports Enabled = true
```

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

I get the notification whenever I click the sync button

### 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
- [ ] (Optional) I have confirmed the issue is not resolved in the latest alpha release ([instructions](https://docs.ankidroid.org/manual.html#betaTesting))