ip lists page: allow a missing description field

Signed-off-by: Nicola Murino <[email protected]>

templates/webadmin/iplists.html

@@ -330,6 +330,7 @@ explicit grant from the SFTPGo Team ([email protected]).
                     {
                         data: "description",
                         visible: true,
+                        defaultContent: "",
                         render: function(data, type, row) {
                             if (type === 'display') {
                                 if (data){