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());
    return LegacyScriptPubKeyMan::AddKeyPubKeyWithDB(batch, secret, pubkey);
}
bool LegacyScriptPubKeyMan::AddKeyPubKeyWithDB(WalletBatch& batch, const CKey& secret, const CPubKey& pubkey)
{
    AssertLockHeld(cs_KeyStore);
    
    assert(!m_storage.IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS));
    
    
    
    bool needsDB = !encrypted_batch;
    if (needsDB) {
        encrypted_batch = &batch;
    }
    if (!AddKeyPubKeyInner(secret, pubkey)) {
        if (needsDB) encrypted_batch = nullptr;
        return false;
    }
    if (needsDB) encrypted_batch = nullptr;
    
    CScript script;
    script = GetScriptForDestination(PKHash(pubkey));
    if (HaveWatchOnly(script)) {
        RemoveWatchOnly(script);
    }
    script = GetScriptForRawPubKey(pubkey);
    if (HaveWatchOnly(script)) {