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);
    vCoins.clear();
    CAmount nTotal = 0;
    
    
    bool allow_used_addresses = !IsWalletFlagSet(WALLET_FLAG_AVOID_REUSE) || (coinControl && !coinControl->m_avoid_address_reuse);
    const int min_depth = {coinControl ? coinControl->m_min_depth : DEFAULT_MIN_DEPTH};
    const int max_depth = {coinControl ? coinControl->m_max_depth : DEFAULT_MAX_DEPTH};
    std::set<uint256> trusted_parents;
    for (const auto& entry : mapWallet)
    {
        const uint256& wtxid = entry.first;
        const CWalletTx& wtx = entry.second;
        if (!locked_chain.checkFinalTx(*wtx.tx)) {
            continue;
        }
        if (wtx.IsImmatureCoinBase())
            continue;
        int nDepth = wtx.GetDepthInMainChain();
        if (nDepth < 0)
            continue;
        
        
        if (nDepth == 0 && !wtx.InMempool())
            continue;
        bool safeTx = wtx.IsTrusted(locked_chain, trusted_parents);