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 :-)
std::map<uint256, CWalletTx>::iterator mi = walletInstance->mapWallet.find(hash);
                if (mi != walletInstance->mapWallet.end())
                {
                    const CWalletTx* copyFrom = &wtxOld;
                    CWalletTx* copyTo = &mi->second;
                    copyTo->mapValue = copyFrom->mapValue;
                    copyTo->vOrderForm = copyFrom->vOrderForm;
                    copyTo->nTimeReceived = copyFrom->nTimeReceived;
                    copyTo->nTimeSmart = copyFrom->nTimeSmart;
                    copyTo->fFromMe = copyFrom->fFromMe;
                    copyTo->strFromAccount = copyFrom->strFromAccount;
                    copyTo->nOrderPos = copyFrom->nOrderPos;
                    batch.WriteTx(*copyTo);
                }
            }
        }
    }
    uiInterface.LoadWallet(walletInstance);
    
    RegisterValidationInterface(walletInstance.get());
    walletInstance->SetBroadcastTransactions(gArgs.GetBoolArg("-walletbroadcast", DEFAULT_WALLETBROADCAST));
    {
        LOCK(walletInstance->cs_wallet);
        LogPrintf("setKeyPool.size() = %u\n",      walletInstance->GetKeyPoolSize());
        LogPrintf("mapWallet.size() = %u\n",       walletInstance->mapWallet.size());
        LogPrintf("mapAddressBook.size() = %u\n",  walletInstance->mapAddressBook.size());
    }
    return walletInstance;
}
void CWallet::postInitProcess()