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).
} else if (!wallet_dir.is_absolute()) {
            chain.initError(strprintf(_("Specified -walletdir \"%s\" is a relative path").translated, wallet_dir.string()));
            return false;
        }
        gArgs.ForceSetArg("-walletdir", canonical_wallet_dir.string());
    }
    LogPrintf("Using wallet directory %s\n", GetWalletDir().string());
    chain.initMessage(_("Verifying wallet(s)...").translated);
    
    
    
    bool salvage_wallet = gArgs.GetBoolArg("-salvagewallet", false) && wallet_files.size() <= 1;
    
    std::set<fs::path> wallet_paths;
    for (const auto& wallet_file : wallet_files) {
        WalletLocation location(wallet_file);
        if (!wallet_paths.insert(location.GetPath()).second) {
            chain.initError(strprintf(_("Error loading wallet %s. Duplicate -wallet filename specified.").translated, wallet_file));
            return false;
        }
        std::string error_string;
        std::vector<std::string> warnings;
        bool verify_success = CWallet::Verify(chain, location, salvage_wallet, error_string, warnings);
        if (!error_string.empty()) chain.initError(error_string);
        if (!warnings.empty()) chain.initWarning(Join(warnings, "\n"));
        if (!verify_success) return false;
    }
    return true;
}
bool LoadWallets(interfaces::Chain& chain, const std::vector<std::string>& wallet_files)