wordpress自定义帖子类型问题 - 自定义帖子页面中的缩略图为行添加了边距

Question

我添加了一个精选图片功能，让精选图片在自定义帖子页面（产品）中显示为缩略图。

问题是图像的div有太多的宽度/填充/边距，这会创建这种视图：

^^^多么可怕，对吧？

以下是我注释的相关功能：

// GET FEATURED IMAGE
function ST4_get_featured_image($post_ID) {
    $post_thumbnail_id = get_post_thumbnail_id($post_ID);
    if ($post_thumbnail_id) {
        $post_thumbnail_img = wp_get_attachment_image_src($post_thumbnail_id, 'featured_preview');
        return $post_thumbnail_img[0];
    }
}
// ADD NEW COLUMN
function ST4_columns_head($defaults) {
    $defaults['featured_image'] = 'Featured Image';
    return $defaults;
}
function ST4_columns_content($column_name, $post_ID) {
    if ($column_name == 'featured_image') {
        $post_featured_image = ST4_get_featured_image($post_ID);
        if ($post_featured_image) {
            // HAS A FEATURED IMAGE
            echo '<img src="' . $post_featured_image . '" />';
        }
        else {
            // NO FEATURED IMAGE, SHOW THE DEFAULT ONE
            echo '<img src="https://placehold.it/60x60?text=insert+pic+here"';
        }
    }
}
add_filter('manage_posts_columns', 'ST4_columns_head');
add_action('manage_posts_custom_column', 'ST4_columns_content', 10, 2);