handle empty menu as inapplicable

Author: Abdillah

src/engine.rs

@@ -855,6 +855,10 @@ impl Reedline {
                 if self.active_menu().is_none() {
                     if let Some(menu) = self.menus.iter_mut().find(|menu| menu.name() == name) {
                         menu.menu_event(MenuEvent::Activate(self.quick_completions));
+                        if menu.get_values().len() == 0 {
+                            menu.menu_event(MenuEvent::Deactivate);
+                            return Ok(EventStatus::Inapplicable);
+                        }
 
                         if self.quick_completions && menu.can_quick_complete() {
                             menu.update_values(