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 (IsWalletLoaded(wallet_path)) {
        error_string = strprintf("Error loading wallet %s. Duplicate -wallet filename specified.", location.GetName());
        return false;
    }
    
    std::unique_ptr<WalletDatabase> database = WalletDatabase::Create(wallet_path);
    try {
        if (!WalletBatch::VerifyEnvironment(wallet_path, error_string)) {
            return false;
        }
    } catch (const fs::filesystem_error& e) {
        error_string = strprintf("Error loading wallet %s. %s", location.GetName(), fsbridge::get_filesystem_error_message(e));
        return false;
    }
    if (salvage_wallet) {
        
        CWallet dummyWallet(&chain, WalletLocation(), WalletDatabase::CreateDummy());
        std::string backup_filename;
        
        
        
        
        auto locked_chain = dummyWallet.LockChain();
        if (!WalletBatch::Recover(wallet_path, (void *)&dummyWallet, WalletBatch::RecoverKeysOnlyFilter, backup_filename)) {
            return false;
        }
    }
    return WalletBatch::VerifyDatabaseFile(wallet_path, warnings, error_string);
}
std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(interfaces::Chain& chain, const WalletLocation& location, std::string& error, std::vector<std::string>& warnings, uint64_t wallet_creation_flags)