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 :-)
{
    DBErrors nZapWalletTxRet = WalletBatch(*database,"cr+").ZapWalletTx(vWtx);
    if (nZapWalletTxRet == DBErrors::NEED_REWRITE)
    {
        if (database->Rewrite("\x04pool"))
        {
            LOCK(cs_wallet);
            setInternalKeyPool.clear();
            setExternalKeyPool.clear();
            m_pool_key_to_index.clear();
            
            
            
        }
    }
    if (nZapWalletTxRet != DBErrors::LOAD_OK)
        return nZapWalletTxRet;
    return DBErrors::LOAD_OK;
}
bool CWallet::SetAddressBook(const CTxDestination& address, const std::string& strName, const std::string& strPurpose)