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 :-)
InitError(_("Prune: last wallet synchronisation goes beyond pruned data. You need to -reindex (download the whole blockchain again in case of pruned node)"));
                return nullptr;
            }
        }
        uiInterface.InitMessage(_("Rescanning..."));
        LogPrintf("Rescanning last %i blocks (from block %i)...\n", chainActive.Height() - pindexRescan->nHeight, pindexRescan->nHeight);
        
        
        while (pindexRescan && walletInstance->nTimeFirstKey && (pindexRescan->GetBlockTime() < (walletInstance->nTimeFirstKey - TIMESTAMP_WINDOW))) {
            pindexRescan = chainActive.Next(pindexRescan);
        }
        nStart = GetTimeMillis();
        {
            WalletRescanReserver reserver(walletInstance.get());
            if (!reserver.reserve()) {
                InitError(_("Failed to rescan the wallet during initialization"));
                return nullptr;
            }
            walletInstance->ScanForWalletTransactions(pindexRescan, nullptr, reserver, true);
        }
        LogPrintf(" rescan      %15dms\n", GetTimeMillis() - nStart);
        walletInstance->ChainStateFlushed(chainActive.GetLocator());
        walletInstance->database->IncrementUpdateCounter();
        
        if (gArgs.GetBoolArg("-zapwallettxes", false) && gArgs.GetArg("-zapwallettxes", "1") != "2")
        {
            WalletBatch batch(*walletInstance->database);
            for (const CWalletTx& wtxOld : vWtx)
            {
                uint256 hash = wtxOld.GetHash();