我想做的是根据是否有帖子缩略图添加一个body类。下面的内容很有效，但我收到了一个PHP通知。如何修复下面的PHP通知？

function add_featured_image_body_class( $classes ) {

    if( has_post_thumbnail() ) {
        $classes[] = \'has-featured-image\';
    }

    return $classes;
}
add_filter( \'body_class\', \'add_featured_image_body_class\' );

PHP注意事项：

PHP Notice:  Trying to get property of non-object in /wp-includes/post-template.php on line 30

这是post模板中的函数。php

function get_the_ID() {
  global $post;
  return $post->ID; // this is line 30
}

Update:

下面是我现在所拥有的，在没有PHP通知的情况下，它似乎可以正常工作

function add_featured_image_body_class( $classes ) {    
    global $post;

    if ( isset ( $post->ID ) && get_the_post_thumbnail($post->ID)) {
      $classes[] = \'has-featured-image\';
    }

    return $classes;
}
add_filter( \'body_class\', \'add_featured_image_body_class\' );

function add_featured_image_body_class( $classes ) {    
global $post;
    if ( isset ( $post->ID ) && get_the_post_thumbnail($post->ID)) {
          $classes[] = \'has-featured-image\';
 }
          return $classes;
}
add_filter( \'body_class\', \'add_featured_image_body_class\' );