### 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_
std::optional<OutputType> GetOutputType() const override { return OutputType::BECH32; }
    bool IsSingleType() const final { return true; }
};
class TRDescriptor final : public DescriptorImpl
{
    std::vector<int> m_depths;
protected:
    std::vector<CScript> MakeScripts(const std::vector<CPubKey>& keys, Span<const CScript> scripts, FlatSigningProvider& out) const override
    {
        TaprootBuilder builder;
        assert(m_depths.size() == scripts.size());
        for (size_t pos = 0; pos < m_depths.size(); ++pos) {
            builder.Add(m_depths[pos], scripts[pos], TAPROOT_LEAF_TAPSCRIPT);
        }
        if (!builder.IsComplete()) return {};
        assert(keys.size() == 1);
        XOnlyPubKey xpk(keys[0]);
        if (!xpk.IsFullyValid()) return {};
        builder.Finalize(xpk);
        WitnessV1Taproot output = builder.GetOutput();
        out.tr_trees[output] = builder;
        out.pubkeys.emplace(keys[0].GetID(), keys[0]);
        return Vector(GetScriptForDestination(output));
    }
    bool ToStringSubScriptHelper(const SigningProvider* arg, std::string& ret, const StringType type, const DescriptorCache* cache = nullptr) const override