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 :-)
CPubKey seed = walletInstance->GenerateNewSeed();
            walletInstance->SetHDSeed(seed);
        }
        
        if (!walletInstance->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS) && !walletInstance->TopUpKeyPool()) {
            InitError(_("Unable to generate initial keys"));
            return nullptr;
        }
        walletInstance->ChainStateFlushed(chainActive.GetLocator());
    } else if (wallet_creation_flags & WALLET_FLAG_DISABLE_PRIVATE_KEYS) {
        
        InitError(strprintf(_("Error loading %s: Private keys can only be disabled during creation"), walletFile));
        return NULL;
    } else if (walletInstance->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
        LOCK(walletInstance->cs_KeyStore);
        if (!walletInstance->mapKeys.empty() || !walletInstance->mapCryptedKeys.empty()) {
            InitWarning(strprintf(_("Warning: Private keys detected in wallet {%s} with disabled private keys"), walletFile));
        }
    } else if (gArgs.IsArgSet("-usehd")) {
        bool useHD = gArgs.GetBoolArg("-usehd", true);
        if (walletInstance->IsHDEnabled() && !useHD) {
            InitError(strprintf(_("Error loading %s: You can't disable HD on an already existing HD wallet"), walletFile));
            return nullptr;
        }
        if (!walletInstance->IsHDEnabled() && useHD) {
            InitError(strprintf(_("Error loading %s: You can't enable HD on an already existing non-HD wallet"), walletFile));
            return nullptr;
        }
    }