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).
{
    AssertLockHeld(cs_wallet);
    unsigned int count = 0;
    for (auto spk_man : GetActiveScriptPubKeyMans()) {
        count += spk_man->KeypoolCountExternalKeys();
    }
    return count;
}
unsigned int CWallet::GetKeyPoolSize() const
{
    AssertLockHeld(cs_wallet);
    unsigned int count = 0;
    for (auto spk_man : GetActiveScriptPubKeyMans()) {
        count += spk_man->GetKeyPoolSize();
    }
    return count;
}
bool CWallet::TopUpKeyPool(unsigned int kpSize)
{
    LOCK(cs_wallet);
    bool res = true;
    for (auto spk_man : GetActiveScriptPubKeyMans()) {
        res &= spk_man->TopUp(kpSize);
    }
    return res;
}
bool CWallet::GetNewDestination(const OutputType type, const std::string label, CTxDestination& dest, std::string& error)