<?php

use Proud\Core;

class AgencyMenu extends Core\ProudWidget {

  function __construct() {
    parent::__construct(
      'agency_menu', // Base ID
      __( 'Agency menu', 'wp-agency' ), // Name
      array( 'description' => __( "Display an agency menu", 'wp-agency' ), ) // Args
    );
  }

  function initialize() {
  }

  /**
   * Outputs the content of the widget
   *
   * @param array $args
   * @param array $instance
   */
  public function printWidget( $args, $instance ) {
      $args = array(
        'menu_class' => 'nav nav-pills nav-stacked',          
      );
      if ('agency' === get_post_type()) {
          if ( $menu = get_post_meta( get_the_ID(), 'post_menu', true ) ) {
              $args['menu'] = $menu;
              wp_nav_menu( $args );
          }
      }
      else {
        global $pageInfo;
        $args = array(
          'menu' => $pageInfo['menu'],
          'menu_class' => 'nav nav-pills nav-stacked',          
        );
        wp_nav_menu( $args );
      }
  }
}

// register Foo_Widget widget
function register_agency_menu_widget() {
    register_widget( 'AgencyMenu' );
}
add_action( 'widgets_init', 'register_agency_menu_widget' );
<?php

use Proud\Core;

class AgencyMenu extends Core\ProudWidget {

  function __construct() {
    parent::__construct(
      'agency_menu', // Base ID
      __( 'Agency menu', 'wp-agency' ), // Name
      array( 'description' => __( "Display an agency menu", 'wp-agency' ), ) // Args
    );
  }

  function initialize() {
  }

  /**
   * Outputs the content of the widget
   *
   * @param array $args
   * @param array $instance
   */
  public function printWidget( $args, $instance ) {
      $args = array(
        'menu_class' => 'nav nav-pills nav-stacked submenu',
        'fallback_cb' => false,
      );
      if ('agency' === get_post_type()) {
          if ( $menu = get_post_meta( get_the_ID(), 'post_menu', true ) ) {
              $args['menu'] = $menu;
              wp_nav_menu( $args );
          }
      }
      else {
        global $pageInfo;
        print_r($pageInfo);die();
        $args = array(
          'menu' => $pageInfo['menu'],
          'menu_class' => 'nav nav-pills nav-stacked',          
        );
        wp_nav_menu( $args );
      }
  }
}

// register Foo_Widget widget
function register_agency_menu_widget() {
    register_widget( 'AgencyMenu' );
}
add_action( 'widgets_init', 'register_agency_menu_widget' );
Set callback param to false
Set callback param to false
