### 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_
{
    for (size_t i = 1; i < split.size(); ++i) {
        Span<const char> elem = split[i];
        bool hardened = false;
        if (elem.size() > 0) {
            const char last = elem[elem.size() - 1];
            if (last == '\'' || last == 'h') {
                elem = elem.first(elem.size() - 1);
                hardened = true;
                apostrophe = last == '\'';
            }
        }
        uint32_t p;
        if (!ParseUInt32(std::string(elem.begin(), elem.end()), &p)) {
            error = strprintf("Key path value '%s' is not a valid uint32", std::string(elem.begin(), elem.end()));
            return false;
        } else if (p > 0x7FFFFFFFUL) {
            error = strprintf("Key path value %u is out of range", p);
            return false;
        }
        out.push_back(p | (((uint32_t)hardened) << 31));
    }
    return true;
}
std::unique_ptr<PubkeyProvider> ParsePubkeyInner(uint32_t key_exp_index, const Span<const char>& sp, ParseScriptContext ctx, FlatSigningProvider& out, bool& apostrophe, std::string& error)