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 :-)
{
    
    
    
    
    
    
    
    
    
    std::map<CTxDestination, std::vector<COutput>> result;
    std::vector<COutput> availableCoins;
    LOCK2(cs_main, cs_wallet);
    AvailableCoins(availableCoins);
    for (auto& coin : availableCoins) {
        CTxDestination address;
        if (coin.fSpendable &&
            ExtractDestination(FindNonChangeParentOutput(*coin.tx->tx, coin.i).scriptPubKey, address)) {
            result[address].emplace_back(std::move(coin));
        }
    }
    std::vector<COutPoint> lockedCoins;
    ListLockedCoins(lockedCoins);
    for (const auto& output : lockedCoins) {
        auto it = mapWallet.find(output.hash);
        if (it != mapWallet.end()) {