以下表达式代码在绝缘节点列为空值时显示“未将对象引用设置到对象的实例”错误,请教怎么修改
For i As Integer = 0 To Tables("软横跨悬挂节点").Rows.Count-1
If i = 0 Then
Dim r As Row = Tables("软横跨悬挂节点").rows(i)
Dim JYLX As DataRow = DataTables("绝缘节点").Find("[节点类型] = '" & r("绝缘节点") & "'")
Dim JYZL As Decimal = IIF(r("绝缘节点") Is Nothing ,JYLX("单横总重"),0)
r("负载计算值") = JYZL
End If
Next