Ticket #44772: 44772.diff

src/wp-includes/post-thumbnail-template.php

@@ -36 +36 @@
  * @return string|int Post thumbnail ID or empty string.
  */
 function get_post_thumbnail_id( $post = null ) {
-        $post = get_post( $post );
-        if ( ! $post ) {
-                return '';
+        if ( ! is_numeric( $post ) ) {
+                $post = get_post( $post );
+
+                if ( ! $post ) {
+                        return '';
+                }
+
+                $post_id = $post->ID;
+        } else {
+                $post_id = $post;
         }
-        return get_post_meta( $post->ID, '_thumbnail_id', true );
+
+        return get_post_meta( $post_id, '_thumbnail_id', true );
 }
 
 /**