### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current behaviour

I randomly encountered this by loading a wallet created from master with an older version. I could trace it down to bd13dc2f46ea10302a928fcf0f53b7aed77ad260 (#26076), but I don't know descriptor wallets enough to understand what's going on (cc @Sjors @achow101).

### Expected behaviour

`bitcoind` starts, or at least tells me to use a later version if #26076 was a breaking change instead of corrupting `wallet.dat`.

### Steps to reproduce

(master, clean chain): 
`createwallet -regtest ""`
(v25.0rc2):
first `bitcoind -regtest` succeeds
then stop and restart the node: The second `bitcoind -regtest` leads to an InitError:
`Error: Error: Unable to expand wallet descriptor from cache`
now, the wallet cannot be loaded by either version.

### Relevant log output

_No response_

### How did you obtain Bitcoin Core

Compiled from source

### What version of Bitcoin Core are you using?

v25.0rc2 / master

### Operating system and version

Ubuntu

### Machine specifications

_No response_
{
    assert(!m_storage.IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS));
    CKey key;
    key.MakeNewKey(true);
    return DeriveNewSeed(key);
}
CPubKey LegacyScriptPubKeyMan::DeriveNewSeed(const CKey& key)
{
    int64_t nCreationTime = GetTime();
    CKeyMetadata metadata(nCreationTime);
    
    CPubKey seed = key.GetPubKey();
    assert(key.VerifyPubKey(seed));
    
    metadata.hdKeypath     = "s";
    metadata.has_key_origin = false;
    metadata.hd_seed_id = seed.GetID();
    {
        LOCK(cs_KeyStore);
        
        mapKeyMetadata[seed.GetID()] = metadata;
        
        if (!AddKeyPubKey(key, seed))
            throw std::runtime_error(std::string(__func__) + ": AddKeyPubKey failed");
    }
    return seed;
}
void LegacyScriptPubKeyMan::SetHDSeed(const CPubKey& seed)