Can't add a wallet when it has 0 wallets

**Bug**
Using a setted up Electrum device, I added a wallet, then deleted it. Now, with 0 wallets on the device, I get an error everytime I try to add a multisig wallet.

**Steps I do to reproduce**
- "Add More Keys"
- "Paste xPub" (I don't even need to paste the xPub, just hitting "continue" it's enough to get the error)
- "Continue"

**Env Information**
- My Node is running locally
- OS: Pop_OS! (ubuntu/debian)
- Specter Version: specter_desktop-v2.0.2-x86_64-linux-gnu

**Screenshots**

**Additional context**
I managed to continue adding a new device with same characteristics and setting up a new wallet into it.

Start by reproducing the “Add More Keys” flow on a device with zero wallets, following the listed steps through “Continue,” and capture the resulting error. Trace that wallet-addition path and consider the issue resolved when adding a multisig wallet works after the existing wallet was deleted, without breaking setup for devices with newly added wallets.

Written by the indexing model from the issue text.