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 :-)
{
    LOCK2(cs_main, cs_wallet);
    int conflictconfirms = 0;
    CBlockIndex* pindex = LookupBlockIndex(hashBlock);
    if (pindex && chainActive.Contains(pindex)) {
        conflictconfirms = -(chainActive.Height() - pindex->nHeight + 1);
    }
    
    
    
    
    if (conflictconfirms >= 0)
        return;
    
    WalletBatch batch(*database, "r+", false);
    std::set<uint256> todo;
    std::set<uint256> done;
    todo.insert(hashTx);