I have 2 legacy wallets and on both if I run `upgradewallet` it will cause bitcoin core to crash. This should just return me an error string

Currenl result from `getwalletinfo`:
```
{
  "walletname": "Wallet",
  "walletversion": 169900,
  "format": "bdb",
  "balance": 0.00000000,
  "unconfirmed_balance": 0.00000000,
  "immature_balance": 0.00000000,
  "txcount": 80,
  "keypoololdest": 1613078825,
  "keypoolsize": 941,
  "keypoolsize_hd_internal": 941,
  "paytxfee": 0.00000000,
  "private_keys_enabled": false,
  "avoid_reuse": true,
  "scanning": false,
  "descriptors": false
}
```
{
    LOCK(cs_KeyStore);
    WalletBatch batch(m_storage.GetDatabase());
    
    int64_t oldestKey = GetOldestKeyTimeInPool(setExternalKeyPool, batch);
    if (IsHDEnabled() && m_storage.CanSupportFeature(FEATURE_HD_SPLIT)) {
        oldestKey = std::max(GetOldestKeyTimeInPool(setInternalKeyPool, batch), oldestKey);
        if (!set_pre_split_keypool.empty()) {
            oldestKey = std::max(GetOldestKeyTimeInPool(set_pre_split_keypool, batch), oldestKey);
        }
    }
    return oldestKey;
}
size_t LegacyScriptPubKeyMan::KeypoolCountExternalKeys() const
{
    LOCK(cs_KeyStore);
    return setExternalKeyPool.size() + set_pre_split_keypool.size();
}
unsigned int LegacyScriptPubKeyMan::GetKeyPoolSize() const
{
    LOCK(cs_KeyStore);
    return setInternalKeyPool.size() + setExternalKeyPool.size() + set_pre_split_keypool.size();
}
int64_t LegacyScriptPubKeyMan::GetTimeFirstKey() const
{
    LOCK(cs_KeyStore);
    return nTimeFirstKey;
}
std::unique_ptr<SigningProvider> LegacyScriptPubKeyMan::GetSolvingProvider(const CScript& script) const