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).
{
    AssertLockHeld(cs_wallet);
    DBErrors nZapSelectTxRet = WalletBatch(*database, "cr+").ZapSelectTx(vHashIn, vHashOut);
    for (uint256 hash : vHashOut) {
        const auto& it = mapWallet.find(hash);
        wtxOrdered.erase(it->second.m_it_wtxOrdered);
        mapWallet.erase(it);
        NotifyTransactionChanged(this, hash, CT_DELETED);
    }
    if (nZapSelectTxRet == DBErrors::NEED_REWRITE)
    {
        if (database->Rewrite("\x04pool"))
        {
            for (const auto& spk_man_pair : m_spk_managers) {
                spk_man_pair.second->RewriteDB();
            }
        }
    }
    if (nZapSelectTxRet != DBErrors::LOAD_OK)
        return nZapSelectTxRet;
    MarkDirty();
    return DBErrors::LOAD_OK;
}
DBErrors CWallet::ZapWalletTx(std::vector<CWalletTx>& vWtx)