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 (!AddToWalletIfInvolvingMe(ptx, pindex, posInBlock, update_tx))
        return; 
    
    
    
    MarkInputsDirty(ptx);
}
void CWallet::TransactionAddedToMempool(const CTransactionRef& ptx) {
    LOCK2(cs_main, cs_wallet);
    SyncTransaction(ptx);
    auto it = mapWallet.find(ptx->GetHash());
    if (it != mapWallet.end()) {
        it->second.fInMempool = true;
    }
}
void CWallet::TransactionRemovedFromMempool(const CTransactionRef &ptx) {