### 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_
{
    LOCK(cs_KeyStore);
    if (keypool.m_pre_split) {
        set_pre_split_keypool.insert(nIndex);
    } else if (keypool.fInternal) {
        setInternalKeyPool.insert(nIndex);
    } else {
        setExternalKeyPool.insert(nIndex);
    }
    m_max_keypool_index = std::max(m_max_keypool_index, nIndex);
    m_pool_key_to_index[keypool.vchPubKey.GetID()] = nIndex;
    
    
    
    CKeyID keyid = keypool.vchPubKey.GetID();
    if (mapKeyMetadata.count(keyid) == 0)
        mapKeyMetadata[keyid] = CKeyMetadata(keypool.nTime);
}
bool LegacyScriptPubKeyMan::CanGenerateKeys() const
{
    
    LOCK(cs_KeyStore);
    return IsHDEnabled() || !m_storage.CanSupportFeature(FEATURE_HD);
}
CPubKey LegacyScriptPubKeyMan::GenerateNewSeed()