message: Fix `mouse_interaction` using wrong layout in `PaneGrid`
  ... when no titlebar is present.
diff: @@ -204,10 +204,9 @@ where
  viewport: &Rectangle,
  cursor_position: Point,
  ) -> mouse::Interaction {
  - let mut children = layout.children();
  -
  let (body_layout, title_bar_interaction) =
  if let Some(title_bar) = &self.title_bar {
  + let mut children = layout.children();
  let title_bar_layout = children.next().unwrap();
  let is_over_pick_area = title_bar
  @@ -225,7 +224,7 @@ where
  (children.next().unwrap(), mouse_interaction)
  } else {
  - (children.next().unwrap(), mouse::Interaction::default())
  + (layout, mouse::Interaction::default())
  };
  self.body
  