### 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_
{
    unsigned char full_key[CPubKey::COMPRESSED_SIZE] = {0x02};
    std::copy(xkey.begin(), xkey.end(), full_key + 1);
    CPubKey pubkey(full_key);
    std::unique_ptr<PubkeyProvider> key_provider = std::make_unique<ConstPubkeyProvider>(0, pubkey, true);
    KeyOriginInfo info;
    if (provider.GetKeyOriginByXOnly(xkey, info)) {
        return std::make_unique<OriginPubkeyProvider>(0, std::move(info), std::move(key_provider), false);
    }
    return key_provider;
}
/**
 * The context for parsing a Miniscript descriptor (either from Script or from its textual representation).
 */
struct KeyParser {
    
    using Key = uint32_t;
    
    FlatSigningProvider* m_out;
    
    const SigningProvider* m_in;
    
    mutable std::vector<std::unique_ptr<PubkeyProvider>> m_keys;
    
    mutable std::string m_key_parsing_error;
    KeyParser(FlatSigningProvider* out LIFETIMEBOUND, const SigningProvider* in LIFETIMEBOUND) : m_out(out), m_in(in) {}