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).
auto locked_chain = chain().lock();
    LOCK(cs_wallet);
    CWalletTx::Confirmation confirm(CWalletTx::Status::UNCONFIRMED,  0, {},  0);
    SyncTransaction(ptx, confirm);
    auto it = mapWallet.find(ptx->GetHash());
    if (it != mapWallet.end()) {
        it->second.fInMempool = true;
    }
}
void CWallet::transactionRemovedFromMempool(const CTransactionRef &ptx) {
    LOCK(cs_wallet);
    auto it = mapWallet.find(ptx->GetHash());
    if (it != mapWallet.end()) {
        it->second.fInMempool = false;
    }
}
void CWallet::blockConnected(const CBlock& block, int height)
{
    const uint256& block_hash = block.GetHash();
    auto locked_chain = chain().lock();
    LOCK(cs_wallet);
    m_last_block_processed_height = height;
    m_last_block_processed = block_hash;
    for (size_t index = 0; index < block.vtx.size(); index++) {
        CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, height, block_hash, index);
        SyncTransaction(block.vtx[index], confirm);
        transactionRemovedFromMempool(block.vtx[index]);
    }
}
void CWallet::blockDisconnected(const CBlock& block, int height)