User preference save throws error ajax-edit

layouts/v7/modules/Users/DetailViewFullContents.tpl

@@ -10,7 +10,11 @@
 
 {* START YOUR IMPLEMENTATION FROM BELOW. Use {debug} for information *}
 {strip}
-    <form id="detailView" data-name-fields='{ZEND_JSON::encode($MODULE_MODEL->getNameFields())}' method="POST">
+	{assign var=NAME_FIELDS value=array('first_name', 'last_name')}
+	{if $MODULE_MODEL}
+		{assign var=NAME_FIELDS value=$MODULE_MODEL->getNameFields()}
+	{/if}
+    <form id="detailView" data-name-fields='{ZEND_JSON::encode($NAME_FIELDS)}' method="POST">
         {include file='DetailViewBlockView.tpl'|@vtemplate_path:$MODULE_NAME RECORD_STRUCTURE=$RECORD_STRUCTURE MODULE_NAME=$MODULE_NAME}
     </form>
 {/strip}