WindowServer: Ensure menu visibility after pushing menu to the stack

We need to make sure the menu was pushed to the open menu stack before
calling set_visible, as this may trigger cursor re-evaluation, which
in turn expects the menu to be considered open.

Fixes #10836

Userland/Services/WindowServer/MenuManager.cpp

@@ -298,6 +298,8 @@ void MenuManager::open_menu(Menu& menu, bool as_current_menu)
 
     m_open_menu_stack.append(menu);
 
+    menu.set_visible(true);
+
     if (!menu.is_empty()) {
         menu.redraw_if_theme_changed();
         auto* window = menu.menu_window();