Events Attribute make required.

function my_required_att(){
	global $EM_Event;

	$EM_Event->event_attribute1 = !empty($_POST['em_attributes']['att1'] ) ? wp_kses($_POST['em_attributes']['att1'], array()):'';

	if( empty($EM_Event->event_attribute1) ){
		$validate_post = false;
		$EM_Event->add_error( __('att1').__(" is required.", "dbem") );
	}

    return $validate_post;
}
add_filter('em_event_validate','my_required_att');