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 (IsDust(newTxOut, discard_rate) || bnb_used)
                    {
                        nChangePosInOut = -1;
                        nFeeRet += nChange;
                    }
                    else
                    {
                        if (nChangePosInOut == -1)
                        {
                            
                            nChangePosInOut = GetRandInt(txNew.vout.size()+1);
                        }
                        else if ((unsigned int)nChangePosInOut > txNew.vout.size())
                        {
                            strFailReason = _("Change index out of range");
                            return false;
                        }
                        std::vector<CTxOut>::iterator position = txNew.vout.begin()+nChangePosInOut;
                        txNew.vout.insert(position, newTxOut);
                    }
                } else {
                    nChangePosInOut = -1;
                }
                
                
                for (const auto& coin : setCoins) {
                    txNew.vin.push_back(CTxIn(coin.outpoint,CScript()));
                }