### 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_
{
protected:
    std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, Span<const CScript>, FlatSigningProvider& out) const override
    {
        CKeyID id = keys[0].GetID();
        out.pubkeys.emplace(id, keys[0]);
        return Vector(GetScriptForDestination(PKHash(id)));
    }
public:
    PKHDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Vector(std::move(prov)), "pkh") {}
    std::optional<OutputType> GetOutputType() const override { return OutputType::LEGACY; }
    bool IsSingleType() const final { return true; }
};
class WPKHDescriptor final : public DescriptorImpl
{
protected:
    std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, Span<const CScript>, FlatSigningProvider& out) const override
    {
        CKeyID id = keys[0].GetID();
        out.pubkeys.emplace(id, keys[0]);
        return Vector(GetScriptForDestination(WitnessV0KeyHash(id)));
    }
public:
    WPKHDescriptor(std::unique_ptr<PubkeyProvider> prov) : DescriptorImpl(Vector(std::move(prov)), "wpkh") {}
    std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32; }
    bool IsSingleType() const final { return true; }
};
class ComboDescriptor final : public DescriptorImpl