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 :-)
{
    CAmount nDebit = 0;
    for (const CTxIn& txin : tx.vin)
    {
        nDebit += GetDebit(txin, filter);
        if (!MoneyRange(nDebit))
            throw std::runtime_error(std::string(__func__) + ": value out of range");
    }
    return nDebit;
}
bool CWallet::IsAllFromMe(const CTransaction& tx, const isminefilter& filter) const
{
    LOCK(cs_wallet);
    for (const CTxIn& txin : tx.vin)
    {
        auto mi = mapWallet.find(txin.prevout.hash);
        if (mi == mapWallet.end())
            return false; 
        const CWalletTx& prev = (*mi).second;
        if (txin.prevout.n >= prev.tx->vout.size())
            return false; 
        if (!(IsMine(prev.tx->vout[txin.prevout.n]) & filter))
            return false;
    }
    return true;
}
CAmount CWallet::GetCredit(const CTransaction& tx, const isminefilter& filter) const