Ticket #39211: 39211.patch

src/wp-includes/post-template.php

@@ -1631 +1631 @@
  * @return bool True on success, false on failure.
  */
 function is_page_template( $template = '' ) {
+        if ( ! is_singular() )
+                return false;
+                
         $page_template = get_page_template_slug( get_queried_object_id() );
 
         if ( empty( $template ) )