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& amount = m_amounts[type];
    if (recalculate || !amount.m_cached[filter]) {
        amount.Set(filter, type == DEBIT ? pwallet->GetDebit(*tx, filter) : pwallet->GetCredit(*tx, filter));
        m_is_cache_empty = false;
    }
    return amount.m_value[filter];
}
CAmount CWalletTx::GetDebit(const isminefilter& filter) const
{
    if (tx->vin.empty())
        return 0;
    CAmount debit = 0;
    if (filter & ISMINE_SPENDABLE) {
        debit += GetCachableAmount(DEBIT, ISMINE_SPENDABLE);
    }
    if (filter & ISMINE_WATCH_ONLY) {
        debit += GetCachableAmount(DEBIT, ISMINE_WATCH_ONLY);
    }
    return debit;
}
CAmount CWalletTx::GetCredit(const isminefilter& filter) const