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).
{
    bool fUpdated = false;
    {
        LOCK(cs_wallet);
        std::map<CTxDestination, CAddressBookData>::iterator mi = mapAddressBook.find(address);
        fUpdated = mi != mapAddressBook.end();
        mapAddressBook[address].name = strName;
        if (!strPurpose.empty()) 
            mapAddressBook[address].purpose = strPurpose;
    }
    NotifyAddressBookChanged(this, address, strName, IsMine(address) != ISMINE_NO,
                             strPurpose, (fUpdated ? CT_UPDATED : CT_NEW) );
    if (!strPurpose.empty() && !batch.WritePurpose(EncodeDestination(address), strPurpose))
        return false;
    return batch.WriteName(EncodeDestination(address), strName);
}
bool CWallet::SetAddressBook(const CTxDestination& address, const std::string& strName, const std::string& strPurpose)