Wordpress Theme Development

Ketika melakukan proses theme development, bagian dashboard tiba-tiba error, muncul peringatan,

Warning: Cannot modify header information - headers already sent by (output started at /home/helokode/public_html/wp-content/themes/helokode/functions.php:24) in /home/helokode/public_html/wp-includes/pluggable.php on line 1207.

Bagaimana solusinya ?