Stop running script if blank

Question

My code is as follows:

Sub Batchcreate()

Dim Session As Object
    Dim r As Integer
    Set Session = SAPFindSession("Cobalt - Z2L (Prod)", useAutoLogon:=False)
    'Set Session = SAPFindSession("Cobalt - ZHL (Cons)", useAutoLogon:=False)
    

For r = 1 To WorksheetFunction.CountA(Columns(1))
Session.findById("wnd[0]/tbar[0]/okcd").Text = "/nmsc1n"
Session.findById("wnd[0]").sendVKey 0
'SAP article number
Session.findById("wnd[0]/usr/subSUBSCR_BATCH_MASTER:SAPLCHRG:1111/subSUBSCR_HEADER:SAPLCHRG:1401/ctxtDFBATCH-MATNR").Text = Cells(r, 1)
Next r
    
End Sub

Excel looks like this:

A1: 12345
A2: 12438
A3: 15463
A4: 15436
A5: _______

A5 is blank, the script continues to try to run even when cell is blank. Can you suggest how to stop script if Cell is blank?

Thank you in advance!