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(event->mimeData()->hasUrls())
        event->acceptProposedAction();
}
void BitcoinGUI::dropEvent(QDropEvent *event)
{
    if(event->mimeData()->hasUrls())
    {
        for (const QUrl &uri : event->mimeData()->urls())
        {
            Q_EMIT receivedURI(uri.toString());
        }
    }
    event->acceptProposedAction();
}
bool BitcoinGUI::eventFilter(QObject *object, QEvent *event)