Issue with the features Module
That error means that $menu_item['page_arguments'][0] isn't an object in the context in which that code is run. It's probably happening during a redirect where the page isn't node/123, and so there's no node object available.

You can fix it by adding a bit of error checking (I've taken the liberty of using menu_get_object() instead of menu_get_item(), it's a more standard way of getting the current node object):

function _MO_events_is_event_page() {
  $is_event = &amp;drupal_static(__FUNCTION__);

  if ($is_event === NULL &amp;&amp; $node = menu_get_object()) {
    $is_event = $node-&gt;type == 'event' || $node-&gt;type == 'virtual_conference';
  }

  return (bool) $is_event;
}