qt: Fix Window -> Minimize menu item

Author: hebasto

src/qt/bitcoingui.cpp

@@ -456,7 +456,7 @@ void BitcoinGUI::createMenuBar()
     QAction* minimize_action = window_menu->addAction(tr("Minimize"));
     minimize_action->setShortcut(QKeySequence(Qt::CTRL + Qt::Key_M));
     connect(minimize_action, &QAction::triggered, [] {
-        qApp->focusWindow()->showMinimized();
+        QApplication::activeWindow()->showMinimized();
     });
     connect(qApp, &QApplication::focusWindowChanged, [minimize_action] (QWindow* window) {
         minimize_action->setEnabled(window != nullptr && (window->flags() & Qt::Dialog) != Qt::Dialog && window->windowState() != Qt::WindowMinimized);