Undefined index: admin_menu in menu_block_view() (line 486 of \modules\menu\menu.module).

Hi,

after the installation of admin_menu "7.x-3.0-rc3+24-dev" I have got an error:
Undefined index: admin_menu in menu_block_view() (line 486 of \modules\menu\menu.module).

With 7.x-3.0-rc1 there were no problems. I have executed "Update.php" and all caches are cleared.
I've got the error on Apache and IIS

code: \modules\menu\menu.module

481 /**
482  * Implements hook_block_view().
483  */
484 function menu_block_view($delta = '') {
485  $menus = menu_get_menus(FALSE);
486  $data['subject'] = check_plain($menus[$delta]);
487  $data['content'] = menu_tree($delta);
488  // Add contextual links for this block.
489  if (!empty($data['content'])) {
490   $data['content']['#contextual_links']['menu'] = array('admin/structure/menu/manage', array($delta));
491  }
492  return $data;
493 }

Thanks in advance