### 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_
{
    LOCK(cs_desc_man);
    std::unordered_set<CScript, SaltedSipHasher> script_pub_keys;
    script_pub_keys.reserve(m_map_script_pub_keys.size());
    for (auto const& [script_pub_key, index] : m_map_script_pub_keys) {
        if (index >= minimum_index) script_pub_keys.insert(script_pub_key);
    }
    return script_pub_keys;
}
int32_t DescriptorScriptPubKeyMan::GetEndRange() const
{
    return m_max_cached_index + 1;
}
bool DescriptorScriptPubKeyMan::GetDescriptorString(std::string& out, const bool priv) const
{
    LOCK(cs_desc_man);
    FlatSigningProvider provider;
    provider.keys = GetKeys();
    if (priv) {
        
        
        
        return m_wallet_descriptor.descriptor->ToPrivateString(provider, out);
    }
    return m_wallet_descriptor.descriptor->ToNormalizedString(provider, out, &m_wallet_descriptor.cache);
}
void DescriptorScriptPubKeyMan::UpgradeDescriptorCache()