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 = LockChain();
    if (locked_chain) {
        Optional<int> block_height = locked_chain->getBlockHeight(wtxIn.m_confirm.hashBlock);
        if (block_height) {
            
            
            wtxIn.m_confirm.block_height = *block_height;
        } else if (wtxIn.isConflicted() || wtxIn.isConfirmed()) {
            
            
            
            
            
            
            wtxIn.setUnconfirmed();
            wtxIn.m_confirm.hashBlock = uint256();
            wtxIn.m_confirm.block_height = 0;
            wtxIn.m_confirm.nIndex = 0;
        }
    }
    uint256 hash = wtxIn.GetHash();
    const auto& ins = mapWallet.emplace(hash, wtxIn);
    CWalletTx& wtx = ins.first->second;
    wtx.BindWallet(this);
    if ( ins.second) {
        wtx.m_it_wtxOrdered = wtxOrdered.insert(std::make_pair(wtx.nOrderPos, &wtx));
    }