### 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_
throw std::runtime_error(std::string(__func__) + ": unknown key in key pool");
        }
        
        if (use_split_keypool && keypool.fInternal != fReturningInternal) {
            throw std::runtime_error(std::string(__func__) + ": keypool entry misclassified");
        }
        if (!keypool.vchPubKey.IsValid()) {
            throw std::runtime_error(std::string(__func__) + ": keypool entry invalid");
        }
        assert(m_index_to_reserved_key.count(nIndex) == 0);
        m_index_to_reserved_key[nIndex] = keypool.vchPubKey.GetID();
        m_pool_key_to_index.erase(keypool.vchPubKey.GetID());
        WalletLogPrintf("keypool reserve %d\n", nIndex);
    }
    NotifyCanGetAddressesChanged();
    return true;
}
void LegacyScriptPubKeyMan::LearnRelatedScripts(const CPubKey& key, OutputType type)
{
    assert(type != OutputType::BECH32M);
    if (key.IsCompressed() && (type == OutputType::P2SH_SEGWIT || type == OutputType::BECH32)) {
        CTxDestination witdest = WitnessV0KeyHash(key.GetID());
        CScript witprog = GetScriptForDestination(witdest);
        
        const auto desc = InferDescriptor(witprog, *this);
        assert(desc && desc->IsSolvable());
        AddCScript(witprog);
    }
}
void LegacyScriptPubKeyMan::LearnAllRelatedScripts(const CPubKey& key)