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 :-)
{
    CMutableTransaction txNew(tx);
    if (!wallet->DummySignTx(txNew, txouts)) {
        
        
        return -1;
    }
    return GetVirtualTransactionSize(txNew);
}
int CalculateMaximumSignedInputSize(const CTxOut& txout, const CWallet* wallet)
{
    CMutableTransaction txn;
    txn.vin.push_back(CTxIn(COutPoint()));
    if (!wallet->DummySignInput(txn.vin[0], txout)) {
        
        
        return -1;
    }
    return GetVirtualTransactionInputSize(txn.vin[0]);
}
void CWalletTx::GetAmounts(std::list<COutputEntry>& listReceived,