Come posso gestire le stringhe vuote in un array? Perchè mi dà errore su: If Not Stringa(3) Is Nothing Then.

Guarda il codice.
codice:
Private Sub cmdModifica_Click(ByVal sender As System.Object, ByVal e 
As System.EventArgs) Handles cmdModifica.Click
        Dim Stringa() As String
        Stringa = Split(List1.SelectedItem, " ")

        Dim A, B, C, D, F As String

        A = Stringa(0)
        B = Stringa(1)
        C = Stringa(2)

        If Not Stringa(3) Is Nothing Then
            D = Stringa(3)
        Else
            D = ""
        End If

        Text1.Text = A
        Text2.Text = B & " " & C & " " & D
End Sub
Grazie.