Invalid characters for a wallet name, e.g. `bitcoin-qt -wallet=你好` used to result in an error like this

<img width="494" alt="schermafbeelding 2018-07-24 om 17 46 37" src="https://user-images.githubusercontent.com/10217/43150553-7bdf598a-8f6a-11e8-8972-44c311a57e56.png">

But now it just crashes:

<img width="509" alt="schermafbeelding 2018-07-24 om 17 43 26" src="https://user-images.githubusercontent.com/10217/43150605-9cf32192-8f6a-11e8-9333-87d074c8dd35.png">

I didn't do a `git bisect`, but it broke somewhere this year :-)
{
    int64_t n = nTimeSmart;
    return n ? n : nTimeReceived;
}
bool CWallet::DummySignInput(CTxIn &tx_in, const CTxOut &txout) const
{
    
    const CScript& scriptPubKey = txout.scriptPubKey;
    SignatureData sigdata;
    if (!ProduceSignature(*this, DUMMY_SIGNATURE_CREATOR, scriptPubKey, sigdata))
    {
        return false;
    } else {
        UpdateInput(tx_in, sigdata);
    }
    return true;
}
bool CWallet::DummySignTx(CMutableTransaction &txNew, const std::vector<CTxOut> &txouts) const