message: [bugfix] IndexBar: Top value calculation error
diff: @@ -103,7 +103,7 @@ export default sfc({
  } else if (index === active - 1) {
  const activeItemTop = rects[active].top - scrollTop;
  item.active = activeItemTop > 0;
  - item.top = activeItemTop - rects[active].height;
  + item.top = activeItemTop - item.height;
  } else {
  item.active = false;
  }
  