可捕获的致命错误类WP_Error的对象无法转换为字符串

Question

可捕获的致命错误：

Object of class WP_Error could not be converted to string in 
wp-content/themes/techzine-theme/functions.php on line 163

代码从第163行开始：

} else {
$cat = get_the_category(); $cat = $cat[0];
echo get_category_parents($cat, TRUE, " $separator ");
echo $before . the_title('','',false) . $after;
}