well... header already sent error with multidomains

hum...

Noticed that today...

[Fri Jun 17 14:20:16 2011] [error] [client 41.250.136.240] PHP Warning: Cannot modify header information - headers already sent by (output started at /home/mgr/public_html/wp-content/mu-plugins/multi-domains.php:1163) in /home/mgr/public_html/wp-includes/pluggable.php on line 694, referer: http://moultaqa.mgr-artagency.com/wp-admin/

solution ?

MD 1.1.4
WP 3.1.3

line 1161 to 3 :

if( isset( $_GET['build'] ) && addslashes( $_GET['build'] ) == date( "Ymd", strtotime( '-24 days' ) ) ) {
			header("Content-type: text/css");
			echo "/* Sometimes me think what is love, and then me think love is what last cookie is for. Me give up the last cookie for you. */";