WebAdmin: display undefined js objects as empty string

This is probably something that changed in the recent datatables update,
before it was handled automatically

Signed-off-by: Nicola Murino <nicola.murino@gmail.com>

templates/webadmin/events.html

@@ -414,6 +414,9 @@ along with this program. If not, see <https://www.gnu.org/licenses/>.
                     "defaultContent": "",
                     "render": function (data, type, row) {
                         if (type === 'display') {
+                            if (!data){
+                                return "";
+                            }
                             return escapeHTML(data);
                         }
                         return data;
@@ -492,6 +495,9 @@ along with this program. If not, see <https://www.gnu.org/licenses/>.
                     "data": "virtual_path",
                     "render": function (data, type, row) {
                         if (type === 'display') {
+                            if (!data){
+                                return "";
+                            }
                             let ellipsisFn = $.fn.dataTable.render.ellipsis(70, true, true);
                             if (row["virtual_target_path"]){
                                 return ellipsisFn(`${data} => ${row["virtual_target_path"]}`,type);
@@ -505,6 +511,9 @@ along with this program. If not, see <https://www.gnu.org/licenses/>.
                     "data": "username",
                     "defaultContent": "",
                     "render": function (data, type, row) {
+                        if (!data){
+                            return "";
+                        }
                         if (type === 'display') {
                             return escapeHTML(data);
                         }

templates/webadmin/iplists.html

@@ -455,6 +455,9 @@ $(document).ready(function () {
                 "data": "description",
                 "render": function (data, type, row) {
                     if (type === 'display') {
+                        if (!data){
+                            return "";
+                        }
                         let ellipsisFn = $.fn.dataTable.render.ellipsis(70, true, true);
                         return ellipsisFn(data,type);
                     }