### 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_
{
    using namespace spanparsing;
    bool permit_uncompressed = ctx == ParseScriptContext::TOP || ctx == ParseScriptContext::P2SH;
    auto split = Split(sp, '/');
    std::string str(split[0].begin(), split[0].end());
    if (str.size() == 0) {
        error = "No key provided";
        return nullptr;
    }
    if (split.size() == 1) {
        if (IsHex(str)) {
            std::vector<unsigned char> data = ParseHex(str);
            CPubKey pubkey(data);
            if (pubkey.IsFullyValid()) {
                if (permit_uncompressed || pubkey.IsCompressed()) {
                    return std::make_unique<ConstPubkeyProvider>(key_exp_index, pubkey, false);
                } else {
                    error = "Uncompressed keys are not allowed";
                    return nullptr;
                }
            } else if (data.size() == 32 && ctx == ParseScriptContext::P2TR) {
                unsigned char fullkey[33] = {0x02};
                std::copy(data.begin(), data.end(), fullkey + 1);
                pubkey.Set(std::begin(fullkey), std::end(fullkey));