If the main window has been minimized to the taskbar (iconified) calling "Show/Hide", "Send" or "Receive" actions from the tray icon menu has no effect: the main window still minimized.

It seems like a Qt bug similar to that old [one](https://bugreports.qt.io/browse/QTBUG-31117).

Tested platform: Linux Mint 19, Qt 5.9.5 / 5.9.6
{
    if (trayIcon)
    {
        trayIcon->setVisible(!fHideTrayIcon);
    }
}
void BitcoinGUI::showModalOverlay()
{
    if (modalOverlay && (progressBar->isVisible() || modalOverlay->isLayerVisible()))
        modalOverlay->toggleVisibility();
}
static bool ThreadSafeMessageBox(BitcoinGUI* gui, const std::string& message, const std::string& caption, unsigned int style)
{
    
    noui_ThreadSafeMessageBox(message, caption, style);
    bool modal = (style & CClientUIInterface::MODAL);
    
    
    style &= ~CClientUIInterface::SECURE;
    bool ret = false;
    
    QMetaObject::invokeMethod(gui, "message",
                               modal ? GUIUtil::blockingGUIThreadConnection() : Qt::QueuedConnection,
                               Q_ARG(QString, QString::fromStdString(caption)),
                               Q_ARG(QString, QString::fromStdString(message)),
                               Q_ARG(unsigned int, style),
                               Q_ARG(bool*, &ret));
    return ret;
}
void BitcoinGUI::subscribeToCoreSignals()