hiddenFieldsets & configFieldsets needs to be defined

layouts/joomla/edit/params.php

@@ -23,17 +23,11 @@
 $extraFields     = $displayData->get('extra_fields') ?: array();
 $tabName         = $displayData->get('tab_name') ?: 'myTab';
 
-if (!empty($displayData->hiddenFieldsets))
-{
-	// These are required to preserve data on save when fields are not displayed.
-	$hiddenFieldsets = $displayData->hiddenFieldsets ?: array();
-}
+// These are required to preserve data on save when fields are not displayed.
+$hiddenFieldsets = $displayData->get('hiddenFieldsets') ?: array();
 
-if (!empty($displayData->configFieldsets))
-{
-	// These are required to configure showing and hiding fields in the editor.
-	$configFieldsets = $displayData->configFieldsets ?: array();
-}
+// These are required to configure showing and hiding fields in the editor.
+$configFieldsets = $displayData->get('configFieldsets') ?: array();
 
 // Handle the hidden fieldsets when show_options is set false
 if (!$displayData->get('show_options', 1))