How to add bottom some values in Listview.Builder?

I need to add General to last. How do I do it? I added a new column to the database. The column name is sortOrder, every other value SortOrder is null without General. SortOrder value is 1 in only General. My API json like this,

{"deF_CAT_ID": 140, "description": "General", "in_use": 1, "sortOrder": 1}

  Widget createListView(BuildContext context, AsyncSnapshot snapshot) {
    List<CategoryItem> values = snapshot.data;
    values.sort((a,b) => a.description.toLowerCase().compareTo(b.description.toLowerCase()));

    int count = 1;
    return Container(
      color: const Color(0xFFFFFFFF),
      child: ListView.builder(
        padding: EdgeInsets.only(top: 8.0, right: 0.0, left: 0.0),
        itemCount: count,
        itemBuilder: (BuildContext context, int index) {
          return GridView.count(
            physics: ScrollPhysics(),
            shrinkWrap: true,
            crossAxisCount: 4,
            children: List.generate(values.length, (index) {
              return GridTile(
                child: GestureDetector(
                  onTap: () => sub(values[index].childId),
                  child: Column(
                    children: [
                      SvgPicture.asset(
                        'assets/images/Defect/icon-${values[index].childId}.svg',
                        height: 50.0,
                       color: Colors.blue,
                      ),
                      Expanded(
                        child: Text(
                          values[index].description,
                          textAlign: TextAlign.center,
                          style: TextStyle(
                              fontSize: 10.0
                          ),),),],),),);}),);},),);}

How about this? If you have multiple values having non-null sortOrder, they are sorted alphabetically.

  values.sort((a, b) {
    if (a.sortOrder == null && b.sortOrder != null) {
      return -1;
    } else if (a.sortOrder != null && b.sortOrder == null) {
      return 1;
    } else {
      return a.description.toLowerCase().compareTo(b.description.toLowerCase());
    }
  });