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).
#include <wallet/load.h>
#include <interfaces/chain.h>
#include <scheduler.h>
#include <util/string.h>
#include <util/system.h>
#include <util/translation.h>
#include <wallet/wallet.h>
bool VerifyWallets(interfaces::Chain& chain, const std::vector<std::string>& wallet_files)
{
    if (gArgs.IsArgSet("-walletdir")) {
        fs::path wallet_dir = gArgs.GetArg("-walletdir", "");
        boost::system::error_code error;
        
        fs::path canonical_wallet_dir = fs::canonical(wallet_dir, error);
        if (error || !fs::exists(wallet_dir)) {
            chain.initError(strprintf(_("Specified -walletdir \"%s\" does not exist").translated, wallet_dir.string()));
            return false;
        } else if (!fs::is_directory(wallet_dir)) {
            chain.initError(strprintf(_("Specified -walletdir \"%s\" is not a directory").translated, wallet_dir.string()));
            return false;