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).
if (nDepth == 0 && wtx.mapValue.count("replaces_txid")) {
            safeTx = false;
        }
        
        
        
        
        
        
        
        
        if (nDepth == 0 && wtx.mapValue.count("replaced_by_txid")) {
            safeTx = false;
        }
        if (fOnlySafe && !safeTx) {
            continue;