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.
#include <qt/modaloverlay.h>
#include <qt/forms/ui_modaloverlay.h>
#include <qt/guiutil.h>
#include <chainparams.h>
#include <QResizeEvent>
#include <QPropertyAnimation>
ModalOverlay::ModalOverlay(QWidget *parent) :
QWidget(parent),
ui(new Ui::ModalOverlay),
bestHeaderHeight(0),
bestHeaderDate(QDateTime()),
layerIsVisible(false),
userClosed(false)
{
    ui->setupUi(this);
    connect(ui->closeButton, &QPushButton::clicked, this, &ModalOverlay::closeClicked);
    if (parent) {
        parent->installEventFilter(this);
        raise();
    }
    blockProcessTime.clear();
    setVisible(false);
}
ModalOverlay::~ModalOverlay()