Ticket #17736: 17736.patch

wp-admin/includes/image-edit.php

@@ -646 +646 @@
 
                 if ( $target == 'thumbnail' || $target == 'all' || $target == 'full' ) {
                         $file_url = wp_get_attachment_url($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";