Rendering panes that do not have $block->title defined causes a PHP notice

Fieldable panel panes do not always define $block->title:

    $block = new stdClass();
    if (empty($settings['extra_fields']['display']) || !empty($settings['extra_fields']['display']['title']['default']['visible'])) {
      $block->title = !empty($entity->title) ? filter_xss_admin($entity->title) : '';
    }
    // If the above if fails, the $block->title is never set.

Notice: Undefined property: stdClass::$title in panels_renderer_editor->render_pane() (line 156 of panels/plugins/display_renderers/panels_renderer_editor.class.php).

While I think fieldable panel panes should always have a block title defined, this is easy to prevent in Panels by changing:

    if (!$block->title) {
      $block->title = t('No title');
    }

To use empty():

    if (empty($block->title)) {
      $block->title = t('No title');
    }