JsonListBuilder-jsonObj is empty list error

[pxz8858]

error at: widget.jsonObj.first

Widget _buildItem(List items) {
if (!isOpened) {
return ClosedJsonObjectItem(
isList: true,
jsonViewTheme: widget.jsonViewTheme,
count: widget.jsonObj.length,
type: Typer.getType(widget.jsonObj.first),
);
}
return Column(
crossAxisAlignment: CrossAxisAlignment.start,
children: items,
);
}