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 :-)
if (outgoing && IsChange(out)) {
                debit -= out.nValue;
            } else if (IsMine(out) & filter && depth >= minDepth && (!account || *account == GetLabelName(out.scriptPubKey))) {
                balance += out.nValue;
            }
        }
        
        if (outgoing && (!account || *account == wtx.strFromAccount)) {
            balance -= debit;
        }
    }
    if (account) {
        balance += WalletBatch(*database).GetAccountCreditDebit(*account);
    }
    return balance;
}
CAmount CWallet::GetAvailableBalance(const CCoinControl* coinControl) const
{
    LOCK2(cs_main, cs_wallet);
    CAmount balance = 0;
    std::vector<COutput> vCoins;
    AvailableCoins(vCoins, true, coinControl);
    for (const COutput& out : vCoins) {
        if (out.fSpendable) {
            balance += out.tx->tx->vout[out.i].nValue;
        }
    }
    return balance;
}
void CWallet::AvailableCoins(std::vector<COutput> &vCoins, bool fOnlySafe, const CCoinControl *coinControl, const CAmount &nMinimumAmount, const CAmount &nMaximumAmount, const CAmount &nMinimumSumAmount, const uint64_t nMaximumCount, const int nMinDepth, const int nMaxDepth) const