message: Simplify check for point in mScrollArea
  A point in the control (not on the border), and not on the slider, is in
  the scroll area.
diff: @@ -168,17 +168,11 @@ void ListBox::onMouseDown(EventHandler::MouseButton /*button*/, int x, int y)
  if (!visible() || mHighlightIndex == constants::NO_SELECTION || mHighlightIndex >= mItems.size()) { return; }
  const auto point = NAS2D::Point{x, y};
  -
  - if (!rect().contains(point))
  + if (!mScrollArea.contains(point))
  {
  return;
  }
  - if (mSlider.visible() && mSlider.rect().contains(point))
  - {
  - return; // if the mouse is on the slider then the slider should handle that
  - }
  -
  setSelected(mHighlightIndex);
  }
  