使用get方法创建控件，用判空吗，例如下面的代码，用判断_listView是否存在吗？

Widget get _listView {
    return ListView(
      children: <Widget>[
        _banner,
        Padding(
          padding: EdgeInsets.fromLTRB(7, 4, 7, 4),
          child: LocalNav(localNavList: localNavList),
        ),
        Padding(
            padding: EdgeInsets.fromLTRB(7, 0, 7, 4),
            child: GridNav(gridNavModel: gridNavModel)),
        Padding(
            padding: EdgeInsets.fromLTRB(7, 0, 7, 4),
            child: SubNav(subNavList: subNavList)),
        Padding(
            padding: EdgeInsets.fromLTRB(7, 0, 7, 4),
            child: SalesBox(salesBox: salesBoxModel)),
      ],
    );
  }