### 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_
}
                if ((path[2] & 0x80000000) == 0) {
                    strErr = strprintf("Unexpected path index of 0x%08x (expected to be greater than or equal to 0x80000000)", path[2]);
                    return DBErrors::NONCRITICAL_ERROR;
                }
                internal = path[1] == (1 | 0x80000000);
                index = path[2] & ~0x80000000;
            }
            
            auto [ins, inserted] = hd_chains.emplace(keyMeta.hd_seed_id, CHDChain());
            CHDChain& chain = ins->second;
            if (inserted) {
                
                chain.nVersion = CHDChain::VERSION_HD_BASE;
                chain.seed_id = keyMeta.hd_seed_id;
            }
            if (internal) {
                chain.nVersion = CHDChain::VERSION_HD_CHAIN_SPLIT;
                chain.nInternalChainCounter = std::max(chain.nInternalChainCounter, index + 1);
            } else {
                chain.nExternalChainCounter = std::max(chain.nExternalChainCounter, index + 1);
            }
        }
        return DBErrors::LOAD_OK;
    });
    result = std::max(result, keymeta_res.m_result);
    
    if (!hd_chains.empty()) {
        LegacyScriptPubKeyMan* legacy_spkm = pwallet->GetLegacyScriptPubKeyMan();
        if (legacy_spkm) {