Debug.rst: Remark about Ggroup in Mail Log

Documentation/Debug.rst

@@ -124,7 +124,10 @@ Mail Log page (Table MailLog)
 -----------------------------
 
 For debugging purposes you may like to add a Mail Log page in the frontend.
-The following QFQ code could be used for that purpose (put it in a QFQ PageContent element)::
+The following QFQ code could be used for that purpose (put it in a QFQ PageContent element)
+
+Note: If you do not use/have the Ggroup table, then remove the "# Filters" block.
+::
 
     # Page parameters
     1.sql = SELECT @grId := '{{grId:C0:digit}}' AS _grId