Object reference not set to an instance of an object

Dim lines() As String
            Dim fields() As String
            Dim li As ListItem = Nothing
            lstValues.Items.Clear()
            lines = "Ett:1|Två:2|Tre:3".Split(CChar("|"))

            For i As Integer = 0 To UBound(lines)
                fields = lines(i).Split(CChar(":"))
          [red]      li.Text = fields(0)[/red]
                li.Value = fields(0)
                lstValues.Items.Add(li)
            Next i

På denna rad: li.Text = fields(0)