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);
    return !mapKeys.empty() || !mapCryptedKeys.empty();
}
void LegacyScriptPubKeyMan::RewriteDB()
{
    LOCK(cs_KeyStore);
    setInternalKeyPool.clear();
    setExternalKeyPool.clear();
    m_pool_key_to_index.clear();
    
    
    
}
static int64_t GetOldestKeyTimeInPool(const std::set<int64_t>& setKeyPool, WalletBatch& batch) {
    if (setKeyPool.empty()) {
        return GetTime();
    }
    CKeyPool keypool;
    int64_t nIndex = *(setKeyPool.begin());
    if (!batch.ReadPool(nIndex, keypool)) {
        throw std::runtime_error(std::string(__func__) + ": read oldest key in keypool failed");
    }
    assert(keypool.vchPubKey.IsValid());
    return keypool.nTime;
}
std::optional<int64_t> LegacyScriptPubKeyMan::GetOldestKeyPoolTime() const