### 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_
{
    WalletBatch batch(m_storage.GetDatabase());
    return AddWatchOnlyWithDB(batch, dest);
}
bool LegacyScriptPubKeyMan::AddWatchOnly(const CScript& dest, int64_t nCreateTime)
{
    m_script_metadata[CScriptID(dest)].nCreateTime = nCreateTime;
    return AddWatchOnly(dest);
}
void LegacyScriptPubKeyMan::LoadHDChain(const CHDChain& chain)
{
    LOCK(cs_KeyStore);
    m_hd_chain = chain;
}
void LegacyScriptPubKeyMan::AddHDChain(const CHDChain& chain)
{
    LOCK(cs_KeyStore);
    
    if (!WalletBatch(m_storage.GetDatabase()).WriteHDChain(chain)) {
        throw std::runtime_error(std::string(__func__) + ": writing chain failed");
    }
    
    if (!m_hd_chain.seed_id.IsNull()) {
        AddInactiveHDChain(m_hd_chain);
    }
    m_hd_chain = chain;
}
void LegacyScriptPubKeyMan::AddInactiveHDChain(const CHDChain& chain)