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 (change_type != OutputType::CHANGE_AUTO) {
        return change_type;
    }
    
    
    if (m_default_address_type == OutputType::LEGACY) {
        return OutputType::LEGACY;
    }
    
    
    for (const auto& recipient : vecSend) {
        
        int witnessversion = 0;
        std::vector<unsigned char> witnessprogram;
        if (recipient.scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram)) {
            return OutputType::BECH32;
        }
    }
    
    return m_default_address_type;
}
bool CWallet::CreateTransaction(const std::vector<CRecipient>& vecSend, CTransactionRef& tx, CReserveKey& reservekey, CAmount& nFeeRet,