(mvc) check if field exists in UImodel grid helper class

src/opnsense/mvc/app/library/OPNsense/Base/UIModelGrid.php

@@ -76,6 +76,7 @@ class UIModelGrid
                 $row =  array();
                 $row['uuid'] = $record->getAttributes()['uuid'];
                 foreach ($fields as $fieldname) {
+                    if ($record->$fieldname != null) {
                         $row[$fieldname] = $record->$fieldname->getNodeData();
                         if (is_array($row[$fieldname])) {
                             foreach ($row[$fieldname] as $fieldKey => $fieldValue) {
@@ -88,6 +89,7 @@ class UIModelGrid
                             }
                         }
                     }
+                }
 
                 // if a search phrase is provided, use it to search in all requested fields
                 if ($searchPhrase != '') {