### 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_
auto desc = ParseScript(key_exp_index, expr, ParseScriptContext::P2SH, out, error);
        if (!desc || expr.size()) return nullptr;
        return std::make_unique<SHDescriptor>(std::move(desc));
    } else if (Func("sh", expr)) {
        error = "Can only have sh() at top level";
        return nullptr;
    }
    if ((ctx == ParseScriptContext::TOP || ctx == ParseScriptContext::P2SH) && Func("wsh", expr)) {
        auto desc = ParseScript(key_exp_index, expr, ParseScriptContext::P2WSH, out, error);
        if (!desc || expr.size()) return nullptr;
        return std::make_unique<WSHDescriptor>(std::move(desc));
    } else if (Func("wsh", expr)) {
        error = "Can only have wsh() at top level or inside sh()";
        return nullptr;
    }
    if (ctx == ParseScriptContext::TOP && Func("addr", expr)) {
        CTxDestination dest = DecodeDestination(std::string(expr.begin(), expr.end()));
        if (!IsValidDestination(dest)) {
            error = "Address is not valid";
            return nullptr;
        }
        return std::make_unique<AddressDescriptor>(std::move(dest));
    } else if (Func("addr", expr)) {
        error = "Can only have addr() at top level";
        return nullptr;
    }
    if (ctx == ParseScriptContext::TOP && Func("tr", expr)) {
        auto arg = Expr(expr);
        auto internal_key = ParsePubkey(key_exp_index, arg, ParseScriptContext::P2TR, out, error);
        if (!internal_key) {