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.
{
    delete ui;
}
bool ModalOverlay::eventFilter(QObject * obj, QEvent * ev) {
    if (obj == parent()) {
        if (ev->type() == QEvent::Resize) {
            QResizeEvent * rev = static_cast<QResizeEvent*>(ev);
            resize(rev->size());
            if (!layerIsVisible)
                setGeometry(0, height(), width(), height());
        }
        else if (ev->type() == QEvent::ChildAdded) {
            raise();
        }
    }
    return QWidget::eventFilter(obj, ev);
}
bool ModalOverlay::event(QEvent* ev) {