Index: functions.php
===================================================================
--- functions.php	(revision 14100)
+++ functions.php	(working copy)
@@ -3421,7 +3421,7 @@
 		if ( $use_cache )
 			$value = wp_cache_get($cache_key, 'site-options');
 
-		if ( false === $value ) {
+		if ( !isset($value) || (false === $value) ) {
 			$value = $wpdb->get_var( $wpdb->prepare("SELECT meta_value FROM $wpdb->sitemeta WHERE meta_key = %s AND site_id = %d", $option, $wpdb->siteid ) );
 
 			if ( is_null($value) )