- Patch #335621 by Dave Reid: fixed warning.

modules/block/block.admin.inc

@@ -391,6 +391,7 @@ function template_preprocess_block_admin_display_form(&$variables) {
       $variables['form'][$i]['region']['#attributes']['class'] = 'block-region-select block-region-' . $region;
       $variables['form'][$i]['weight']['#attributes']['class'] = 'block-weight block-weight-' . $region;
 
+      $variables['block_listing'][$region][$i] = new stdClass();
       $variables['block_listing'][$region][$i]->row_class = isset($block['#attributes']['class']) ? $block['#attributes']['class'] : '';
       $variables['block_listing'][$region][$i]->block_modified = isset($block['#attributes']['class']) && strpos($block['#attributes']['class'], 'block-modified') !== FALSE;
       $variables['block_listing'][$region][$i]->block_title =  drupal_render($block['info']);