Noticed this while reviewing #13529, but it's also in master @ 5ba77df15. On macOS 10.13.6:

```
bitcoin-qt -disablewallet
```

<img width="1354" alt="schermafbeelding 2018-08-01 om 16 03 41" src="https://user-images.githubusercontent.com/10217/43526506-b23264d8-95a4-11e8-81a0-5debcad838ae.png">

The usual progress modal doesn't appear when QT starts, and clicking on the progress bar has no effect. It works fine when there's a wallet present.
{
    if (nProgress == 0)
    {
        progressDialog = new QProgressDialog(title, "", 0, 100);
        progressDialog->setWindowModality(Qt::ApplicationModal);
        progressDialog->setMinimumDuration(0);
        progressDialog->setCancelButton(0);
        progressDialog->setAutoClose(false);
        progressDialog->setValue(0);
    }
    else if (nProgress == 100)
    {
        if (progressDialog)
        {
            progressDialog->close();
            progressDialog->deleteLater();
        }
    }
    else if (progressDialog)
        progressDialog->setValue(nProgress);
}
void BitcoinGUI::setTrayIconVisible(bool fHideTrayIcon)