Opening two of the same wallet (tested in v0.18.0 of bitcoin-qt 64 bit) will cause a database collision, and will crash the program.

`[marshall@likon] {21:21} [~] $ bitcoin-0.18.0/bin/bitcoin-qt `
`terminate called after throwing an instance of 'std::runtime_error'  what():  BerkeleyBatch: Can't open database 8204388-wallet.dat (duplicates fileid 8b1c090000000800e25686350000000000000000 from 1352491-wallet.dat)`
`Aborted (core dumped)`

I have been able to reproduce the issue by importing two of the same wallet (with different filenames).
if (nLoadWalletRet == DBErrors::CORRUPT) {
            error = strprintf(_("Error loading %s: Wallet corrupted").translated, walletFile);
            return nullptr;
        }
        else if (nLoadWalletRet == DBErrors::NONCRITICAL_ERROR)
        {
            warnings.push_back(strprintf(_("Error reading %s! All keys read correctly, but transaction data"
                                          " or address book entries might be missing or incorrect.").translated,
                walletFile));
        }
        else if (nLoadWalletRet == DBErrors::TOO_NEW) {
            error = strprintf(_("Error loading %s: Wallet requires newer version of %s").translated, walletFile, PACKAGE_NAME);
            return nullptr;
        }
        else if (nLoadWalletRet == DBErrors::NEED_REWRITE)
        {
            error = strprintf(_("Wallet needed to be rewritten: restart %s to complete").translated, PACKAGE_NAME);
            return nullptr;
        }
        else {
            error = strprintf(_("Error loading %s").translated, walletFile);
            return nullptr;
        }
    }
    int prev_version = walletInstance->GetVersion();
    if (gArgs.GetBoolArg("-upgradewallet", fFirstRun))
    {
        int nMaxVersion = gArgs.GetArg("-upgradewallet", 0);
        if (nMaxVersion == 0) 
        {