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 :-)
{
    const std::string& walletFile = name;
    
    std::vector<CWalletTx> vWtx;
    if (gArgs.GetBoolArg("-zapwallettxes", false)) {
        uiInterface.InitMessage(_("Zapping all transactions from wallet..."));
        std::unique_ptr<CWallet> tempWallet = MakeUnique<CWallet>(name, WalletDatabase::Create(path));
        DBErrors nZapWalletRet = tempWallet->ZapWalletTx(vWtx);
        if (nZapWalletRet != DBErrors::LOAD_OK) {
            InitError(strprintf(_("Error loading %s: Wallet corrupted"), walletFile));
            return nullptr;
        }
    }
    uiInterface.InitMessage(_("Loading wallet..."));
    int64_t nStart = GetTimeMillis();
    bool fFirstRun = true;
    
    
    std::shared_ptr<CWallet> walletInstance(new CWallet(name, WalletDatabase::Create(path)), ReleaseWallet);
    DBErrors nLoadWalletRet = walletInstance->LoadWallet(fFirstRun);
    if (nLoadWalletRet != DBErrors::LOAD_OK)
    {
        if (nLoadWalletRet == DBErrors::CORRUPT) {
            InitError(strprintf(_("Error loading %s: Wallet corrupted"), walletFile));