라인을 찾아보면 그 내용은 다음과 같고요 (마지막 줄이 20번째 라인입니다):

어떤 해결 방법이 있을까요?
 

<?php
class FairEdgeStickySidebar extends FairEdgeWidget {
 protected $params;
 public function __construct() {
  parent::__construct(
   'edgtf_sticky_sidebar', // Base ID
   'Edge Sticky Sidebar', // Name
   array( 'description' => esc_html__( 'Use this widget to make the sidebar sticky. Drag it into the sidebar above the widget which you want to be the first element in the sticky sidebar.', 'fair' ), ) // Args
  );
  $this->setParams();
 }
 protected function setParams() {
  
 }
 public function widget( $args, $instance ) {
  echo '<div class="widget widget_sticky-sidebar"></div>';
 }

}
add_action( 'widgets_init', create_function( '', 'register_widget( "FairEdgeStickySidebar" );' ) );