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 :-)
{
        CScriptID id;
        CRIPEMD160().Write(scriptID.begin(), 32).Finalize(id.begin());
        CScript script;
        if (keystore.GetCScript(id, script)) {
            Process(script);
        }
    }
    void operator()(const WitnessV0KeyHash& keyid)
    {
        CKeyID id(keyid);
        if (keystore.HaveKey(id)) {
            vKeys.push_back(id);
        }
    }
    template<typename X>
    void operator()(const X &none) {}
};
const CWalletTx* CWallet::GetWalletTx(const uint256& hash) const
{
    LOCK(cs_wallet);
    std::map<uint256, CWalletTx>::const_iterator it = mapWallet.find(hash);
    if (it == mapWallet.end())
        return nullptr;
    return &(it->second);
}
CPubKey CWallet::GenerateNewKey(WalletBatch &batch, bool internal)