himeka

Thank you @arnaudbroes.

I hope this problem will be resolved.

I decided to disable WP_DEBUG in the wp-config.php file.

Thank you.
I have set the WordPress “Static Front Page” option.
The error on line 1105 has disappeared, but the error on line 805 has not disappeared …
Is there anything else you can think of?

Thank you for your answer.

This error occurs on the post list page in archive.php.

The customizations that appear to be influenced by function.php are:

/**
 * @param string $breadcrumb_trail .
 */
function my_static_breadcrumb_adder( $breadcrumb_trail ) {
    if ( is_search() || get_post_type() === 'post' ) {
        $item                            = new bcn_breadcrumb( 'SIOSDX Blog', '', array( '' ), home_url( 'blog' ), null, true );
        $stuck                           = array_pop( $breadcrumb_trail->breadcrumbs );
        $breadcrumb_trail->breadcrumbs[] = $item;
        $breadcrumb_trail->breadcrumbs[] = $stuck;
    }
    if ( is_tag() ) {
        $item     = new bcn_breadcrumb( 'tags', '', array( '' ), null, null, true );
        $tag_name = array_shift( $breadcrumb_trail->breadcrumbs );
        array_unshift( $breadcrumb_trail->breadcrumbs, $tag_name, $item );
    }
    if ( is_singular( 'solution' ) ) {
        if ( 5 === count( $breadcrumb_trail->trail ) ) {
            unset( $breadcrumb_trail->trail[1] );
        }
    }
}
/**
 * @param string $args .
 * @param string $post_type .
 */
function post_has_archive( $args, $post_type ) {
    if ( 'post' === $post_type ) {
        $args['rewrite']     = true;
        $args['has_archive'] = 'blog';
    }
    return $args;
}
add_filter( 'register_post_type_args', 'post_has_archive', 10, 2 );
/**
 * @param string $permalink .
 */
function add_article_post_permalink( $permalink ) {
    // デフォルトの投稿の記事詳細に<code>/blog/</code>(アーカイブ名)を追加する .
    $permalink = '/blog' . $permalink;
    return $permalink;
}
add_filter( 'pre_post_link', 'add_article_post_permalink' );
/**
 * リライトルール
 */
add_rewrite_rule( 'blog/([^/]+)/?$', 'index.php?category_name=$matches[1]', 'top' );
add_rewrite_rule( 'blog/tags/([^/]+)/?$', 'index.php?tag=$matches[1]', 'top' );
add_rewrite_rule( 'blog/([^/]+)/page/([0-9]+)/?$', 'index.php?category_name=$matches[1]&paged=$matches[2]', 'top' );

ご返信ありがとうございます。承知いたしました。
使用させていただきます。