variable Classification throwing null value, not thowing the output labels

[dzikrifazahk]

if (classification != null)
...(classification!.entries.toList()
..sort(
(a, b) => a.value.compareTo(b.value),
))
.reversed
.take(3)
.map(
(e) => Container(
padding: const EdgeInsets.all(8),
color: Colors.white,
child: Row(
children: [
Text(e.key),
const Spacer(),
Text(e.value.toStringAsFixed(2))
],
),
),
),