diff --git a/modules/post-type/meta/base-meta-type.php b/modules/post-type/meta/base-meta-type.php
index 3d0b957b..46579f27 100644
--- a/modules/post-type/meta/base-meta-type.php
+++ b/modules/post-type/meta/base-meta-type.php
@@ -32,7 +32,8 @@ public function query( $form_id ) {
 		}
 		$form = get_post( $form_id );
 
-		if ( $form->post_parent ) {
+		// compatibility for preview the form
+		if ( $form && $form->post_parent ) {
 			$form_id = $form->post_parent;
 		}