Ticket #17736: 17736.2.diff

wp-admin/includes/image-edit.php

@@ -708 +708 @@
                                 $return->thumbnail = $thumb_url[0];
                         } else {
                                 $file_url = wp_get_attachment_url($post_id);
-                                if ( $thumb = $meta['sizes']['thumbnail'] )
+                                if ( !empty( $meta['sizes']['thumbnail'] ) && $thumb = $meta['sizes']['thumbnail'] )
                                         $return->thumbnail = path_join( dirname($file_url), $thumb['file'] );
                                 else
                                         $return->thumbnail = "$file_url?w=128&h=128";