Trigger the wp_print_syles action from wp_print_styles() only when handles are not passed. Prevents front-end styles from leaking into the admin. Props nacin. see #19510 for trunk

git-svn-id: http://svn.automattic.com/wordpress/trunk@19649 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/functions.wp-styles.php

@@ -18,10 +18,12 @@
  * @return bool True on success, false on failure.
  */
 function wp_print_styles( $handles = false ) {
-	do_action( 'wp_print_styles' );
 	if ( '' === $handles ) // for wp_head
 		$handles = false;
 
+	if ( ! $handles )
+		do_action( 'wp_print_styles' );
+
 	global $wp_styles;
 	if ( ! is_a( $wp_styles, 'WP_Styles' ) ) {
 		if ( ! did_action( 'init' ) )