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 (!passphrase.empty() && !(wallet_creation_flags & WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
        if (!wallet->EncryptWallet(passphrase)) {
            error = "Error: Wallet created but failed to encrypt.";
            return WalletCreationStatus::ENCRYPTION_FAILED;
        }
        if (!create_blank) {
            
            if (!wallet->Unlock(passphrase)) {
                error = "Error: Wallet was encrypted but could not be unlocked";
                return WalletCreationStatus::ENCRYPTION_FAILED;
            }
            
            {
                LOCK(wallet->cs_wallet);
                for (auto spk_man : wallet->GetActiveScriptPubKeyMans()) {
                    if (!spk_man->SetupGeneration()) {
                        error = "Unable to generate initial keys";
                        return WalletCreationStatus::CREATION_FAILED;
                    }
                }
            }
            
            wallet->Lock();
        }
    }
    AddWallet(wallet);
    wallet->postInitProcess();
    result = wallet;
    return WalletCreationStatus::SUCCESS;
}