Code stop working after exit Sub

Good day everyone,
I am having problem figuring out why my Excel stops working if a cell is empty. What is wrong?

Private Sub CommandButton1_Click()
Application.ScreenUpdating = False
Application.EnableEvents = False

If IsEmpty(ActiveCell) Then
MsgBox "Selected cell is empty. ", vbExclamation, "No Requisition Number"
Unload Me
Exit Sub
End If

'other codes here

Application.ScreenUpdating = True
Application.EnableEvents = True

End Sub

The code just stop working after this is run without anything in the selected cell.

Should I remove something...but what.

The msg pops up but once I have selected "Ok" all codes in my workbook stops working.