Compile master, and run with `src/qt/bitcoin-qt -regtest -nowallet`. As expected, no icon is displayed. Load and unload a wallet. The `HD` icon remains.

On startup:
![on_startup](https://user-images.githubusercontent.com/863730/72410834-711b4c00-37a4-11ea-9a10-bfcf3db7ce68.png)

After a wallet load and unload:
![after_load_unload](https://user-images.githubusercontent.com/863730/72410838-737da600-37a4-11ea-8854-dd13301c0135.png)

#include <QDateTime>
#include <QDragEnterEvent>
#include <QListWidget>
#include <QMenu>
#include <QMenuBar>
#include <QMessageBox>
#include <QMimeData>
#include <QProgressDialog>
#include <QScreen>
#include <QSettings>
#include <QShortcut>
#include <QStackedWidget>
#include <QStatusBar>
#include <QStyle>
#include <QSystemTrayIcon>
#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) :