### 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_
/** Expand a descriptor at a specified position.
     *
     * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
     * @param[in] provider The provider to query for private keys in case of hardened derivation.
     * @param[out] output_scripts The expanded scriptPubKeys.
     * @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`).
     * @param[out] write_cache Cache data necessary to evaluate the descriptor at this point without access to private keys.
     */
    virtual bool Expand(int pos, const SigningProvider& provider, std::vector<CScript>& output_scripts, FlatSigningProvider& out, DescriptorCache* write_cache = nullptr) const = 0;
    /** Expand a descriptor at a specified position using cached expansion data.
     *
     * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
     * @param[in] read_cache Cached expansion data.
     * @param[out] output_scripts The expanded scriptPubKeys.
     * @param[out] out Scripts and public keys necessary for solving the expanded scriptPubKeys (may be equal to `provider`).
     */
    virtual bool ExpandFromCache(int pos, const DescriptorCache& read_cache, std::vector<CScript>& output_scripts, FlatSigningProvider& out) const = 0;
    /** Expand the private key for a descriptor at a specified position, if possible.
     *
     * @param[in] pos The position at which to expand the descriptor. If IsRange() is false, this is ignored.
     * @param[in] provider The provider to query for the private keys.
     * @param[out] out Any private keys available for the specified `pos`.
     */
    virtual void ExpandPrivate(int pos, const SigningProvider& provider, FlatSigningProvider& out) const = 0;
    
    virtual std::optional<OutputType> GetOutputType() const = 0;
};
/** Parse a `descriptor` string. Included private keys are put in `out`.
 *
 * If the descriptor has a checksum, it must be valid. If `require_checksum`