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 <QApplication>
#include <QComboBox>
#include <QDateTime>
#include <QDesktopWidget>
#include <QDragEnterEvent>
#include <QListWidget>
#include <QMenuBar>
#include <QMessageBox>
#include <QMimeData>
#include <QProgressDialog>
#include <QSettings>
#include <QShortcut>
#include <QStackedWidget>
#include <QStatusBar>
#include <QStyle>
#include <QTimer>
#include <QToolBar>
#include <QUrlQuery>
#include <QVBoxLayout>
#include <QWindow>
const std::string BitcoinGUI::DEFAULT_UIPLATFORM =
#if defined(Q_OS_MAC)
        "macosx"
#elif defined(Q_OS_WIN)
        "windows"
#else
        "other"
#endif
        ;
BitcoinGUI::BitcoinGUI(interfaces::Node& node, const PlatformStyle *_platformStyle, const NetworkStyle *networkStyle, QWidget *parent) :