You might check if the worksheet name exists before trying to add it.
Function Test_WorkSheetExists()  
  MsgBox "WorksheetExists? " & WorkSheetExists("Sheet1"), _
    vbInformation, "ActiveWorkbook.ActiveSheet"
End Function


 'WorkSheetExists in a workbook:
Function WorkSheetExists(sWorkSheet As String, Optional sWorkbook As String = "") As Boolean
    Dim ws As Worksheet, wb As Workbook
    On Error GoTo notExists
    If sWorkbook = "" Then
      Set wb = ActiveWorkbook
      Else
      Set wb = Workbooks(sWorkbook)
    End If
    Set ws = wb.Worksheets(sWorkSheet)
    WorkSheetExists = True
    Exit Function
notExists:
    WorkSheetExists = False
End Function