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)

{
#ifndef Q_OS_MAC
    
    if (!trayIcon)
        return;
    trayIcon->setContextMenu(trayIconMenu.get());
    connect(trayIcon, &QSystemTrayIcon::activated, this, &BitcoinGUI::trayIconActivated);
#else
    
    MacDockIconHandler *dockIconHandler = MacDockIconHandler::instance();
    connect(dockIconHandler, &MacDockIconHandler::dockIconClicked, this, &BitcoinGUI::macosDockIconActivated);
    trayIconMenu->setAsDockMenu();
#endif
    
#ifndef Q_OS_MAC
    
    trayIconMenu->addAction(toggleHideAction);
    trayIconMenu->addSeparator();
#endif
    if (enableWallet) {
        trayIconMenu->addAction(sendCoinsMenuAction);
        trayIconMenu->addAction(receiveCoinsMenuAction);
        trayIconMenu->addSeparator();
        trayIconMenu->addAction(signMessageAction);
        trayIconMenu->addAction(verifyMessageAction);