message: Use `Menu::default` for root level menu in `conversion::menu`
diff: @@ -179,11 +179,11 @@ fn hotkey(hotkey: keyboard::Hotkey) -> winit::window::Hotkey {
  /// [`iced_native`]: https://github.com/hecrj/iced/tree/master/native
  pub fn menu<Message>(menu: &Menu<Message>) -> winit::window::Menu {
  fn menu_i<Message>(
  + converted: &mut winit::window::Menu,
  starting_id: usize,
  menu: &Menu<Message>,
  - ) -> (winit::window::Menu, usize) {
  + ) -> usize {
  let mut id = starting_id;
  - let mut converted = winit::window::Menu::new();
  for item in menu.iter() {
  match item {
  @@ -195,9 +195,11 @@ pub fn menu<Message>(menu: &Menu<Message>) -> winit::window::Menu {
  id += 1;
  }
  menu::Entry::Dropdown { content, submenu } => {
  - let (submenu, n_children) = menu_i(id, submenu);
  + let mut converted_submenu = winit::window::Menu::new();
  + let n_children =
  + menu_i(&mut converted_submenu, id, submenu);
  - converted.add_dropdown(content, submenu);
  + converted.add_dropdown(content, converted_submenu);
  id += n_children;
  }
  @@ -207,10 +209,11 @@ pub fn menu<Message>(menu: &Menu<Message>) -> winit::window::Menu {
  }
  }
  - (converted, id - starting_id)
  + id - starting_id
  }
  - let (converted, _) = menu_i(0, menu);
  + let mut converted = winit::window::Menu::default();
  + let _ = menu_i(&mut converted, 0, menu);
  converted
  }
  