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).
{
    LOCK(cs_wallet);
    
    if (nWalletVersion > nVersion)
        return false;
    nWalletMaxVersion = nVersion;
    return true;
}
std::set<uint256> CWallet::GetConflicts(const uint256& txid) const
{
    std::set<uint256> result;
    AssertLockHeld(cs_wallet);
    std::map<uint256, CWalletTx>::const_iterator it = mapWallet.find(txid);
    if (it == mapWallet.end())
        return result;
    const CWalletTx& wtx = it->second;
    std::pair<TxSpends::const_iterator, TxSpends::const_iterator> range;
    for (const CTxIn& txin : wtx.tx->vin)
    {
        if (mapTxSpends.count(txin.prevout) <= 1)
            continue;  
        range = mapTxSpends.equal_range(txin.prevout);
        for (TxSpends::const_iterator _it = range.first; _it != range.second; ++_it)
            result.insert(_it->second);
    }
    return result;
}
bool CWallet::HasWalletSpend(const uint256& txid) const