I only want the values ​​greater than 0 to be visible. It gives the following error, how can I fix it? Because if I don’t do it this way, if I use else and suppress SizedBox(), CupertinoListSection shows empty divider.

Statements in an if should be enclosed in a block. (Documentation)
Try wrapping the statement in a block.

FutureBuilder(
  future: item.assetCountAsync,
  builder:
      (BuildContext context, AsyncSnapshot<int> snapshot) {
    if (snapshot.connectionState ==
        ConnectionState.waiting) {
      return const SizedBox();
    } else {
      if(snapshot.data != null && snapshot.data! > 0) // snapshot.data! > 0
        return CupertinoListTile.notched(
            onTap: () {
              Navigator.pop(context, item);
            },
            title: Text(item.name),
            additionalInfo: Text(snapshot.data.toString()));
    }
  },
)