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
}
```
{
    return std::make_unique<LegacySigningProvider>(*this);
}
bool LegacyScriptPubKeyMan::CanProvide(const CScript& script, SignatureData& sigdata)
{
    IsMineResult ismine = IsMineInner(*this, script, IsMineSigVersion::TOP,  false);
    if (ismine == IsMineResult::SPENDABLE || ismine == IsMineResult::WATCH_ONLY) {
        
        
        
        return true;
    } else {
        
        ProduceSignature(*this, DUMMY_SIGNATURE_CREATOR, script, sigdata);
        if (!sigdata.signatures.empty()) {
            
            bool has_privkeys = false;
            for (const auto& key_sig_pair : sigdata.signatures) {
                has_privkeys |= HaveKey(key_sig_pair.first);
            }
            return has_privkeys;
        }
        return false;
    }
}
bool LegacyScriptPubKeyMan::SignTransaction(CMutableTransaction& tx, const std::map<COutPoint, Coin>& coins, int sighash, std::map<int, bilingual_str>& input_errors) const