### 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);
    setWatchOnly.insert(dest);
    CPubKey pubKey;
    if (ExtractPubKey(dest, pubKey)) {
        mapWatchKeys[pubKey.GetID()] = pubKey;
        ImplicitlyLearnRelatedKeyScripts(pubKey);
    }
    return true;
}
bool LegacyScriptPubKeyMan::AddWatchOnlyWithDB(WalletBatch &batch, const CScript& dest)
{
    if (!AddWatchOnlyInMem(dest))
        return false;
    const CKeyMetadata& meta = m_script_metadata[CScriptID(dest)];
    UpdateTimeFirstKey(meta.nCreateTime);
    NotifyWatchonlyChanged(true);
    if (batch.WriteWatchOnly(dest, meta)) {
        m_storage.UnsetBlankWalletFlag(batch);
        return true;
    }
    return false;
}
bool LegacyScriptPubKeyMan::AddWatchOnlyWithDB(WalletBatch &batch, const CScript& dest, int64_t create_time)
{
    m_script_metadata[CScriptID(dest)].nCreateTime = create_time;
    return AddWatchOnlyWithDB(batch, dest);
}
bool LegacyScriptPubKeyMan::AddWatchOnly(const CScript& dest)