Adding Required Image when submitting an event

/**
This snippet will make featured image required when submitting new events.
*/
function em_validate($result,$EM_Event){
 global $EM_Notices;
 $image = $EM_Event->get_image_url();
 if ( empty($image) && !is_admin()){
  $EM_Event->add_error('image is required.');
 }
}
add_filter('em_event_validate_meta','em_validate',10,2);