我的自定义元框有一个下拉字段，但如何将默认选项值设置为空？它目前正在通过CPT的meta\\u值进行填充，但我希望这有所改变。

以下是该问题的截图：

我希望第二作者字段的第一个选项为空/没有选择。

元框代码：

            case \'select\' :
                $author_select_query = new WP_Query(array(
                    \'post_type\' => \'people\',
                    \'tax_query\' => array(
                        \'relation\' => \'OR\',
                        array(
                            \'taxonomy\' => \'role\',
                            \'field\' => \'slug\',
                            \'terms\' => array(\'adjunct-faculty\'),
                        ),
                        array(
                            \'taxonomy\' => \'role\',
                            \'field\' => \'slug\',
                            \'terms\' => array(\'faculty\'),
                        )
                    ),
                    \'meta_key\' => \'ecpt_people_alpha\',
                    \'orderby\' => \'meta_value\',
                    \'order\' => \'ASC\',
                    \'posts_per_page\' => \'-1\')); 
                $authors = $author_select_query ->get_posts();
                echo \'<select name="\', $field[\'id\'], \'" id="\', $field[\'id\'], \'">\';
                foreach($authors as $author) {
                    echo \'<option value="\' . $author->ID . \'"\', $meta == $author->ID ? \' selected="selected"\' : \'\', \'>\', $author->post_title, \'</option>\';
                }
                echo \'</select>\';