Ticket #38374: 38374.diff

src/wp-includes/template.php

@@ -135 +135 @@
                 $post_type = reset( $post_type );
 
         $obj = get_post_type_object( $post_type );
-        if ( ! $obj->has_archive )
+        if ( ! ( $obj instanceof WP_Post_Type ) || ! $obj->has_archive ) {
                 return '';
+        }
 
         return get_archive_template();
 }