URL encode the theme stylesheet passed into wp_customize_url(). see #21749.

git-svn-id: http://core.svn.wordpress.org/trunk@21713 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/theme.php

@@ -1646,11 +1646,12 @@ add_action( 'admin_enqueue_scripts', '_wp_customize_loader_settings' );
  * @since 3.4.0
  *
  * @param string $stylesheet Optional. Theme to customize. Defaults to current theme.
+ * 	The theme's stylesheet will be urlencoded if necessary.
  */
 function wp_customize_url( $stylesheet = null ) {
 	$url = admin_url( 'customize.php' );
 	if ( $stylesheet )
-		$url .= '?theme=' . $stylesheet;
+		$url .= '?theme=' . urlencode( $stylesheet );
 	return esc_url( $url );
 }