Identifng A Blank Cell Using VBA (Target.value)

I have a piece of code that does the following:

In Cell A1 if 0 is entered, it puts a diagonal line through the cell

If in Cell A1 anything other than a 0 is entered, then the the diagonal disappears.

I would like however for the code to recognize that if the cell is blank then to put a diagonal line through the cell as opposed to entering a 0. The code is listed below:

*The code below also does what is described above for cell A2*
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Private Sub Worksheet_Change(ByVal Target As Range)
Select Case Target.Address

Case "$A$1"
If Target.Value = 0 Then
Target.Select
With Selection.Borders(xlDiagonalUp)
.LineStyle = xlContinuous
.Weight = xlThin
.ColorIndex = xlAutomatic
End With