From eaa89a4da71b3b1d22881b9e76993f79fa6f3c9e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bar=C4=B1=C5=9F=20Soner=20U=C5=9Fakl=C4=B1?=
 <barisusakli@gmail.com>
Date: Thu, 7 May 2015 14:23:03 -0400
Subject: [PATCH] added checks to skip empty/non-existing hashes

---
 src/upgrade.js | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/upgrade.js b/src/upgrade.js
index 3b9492b94b..da5edb4a36 100644
--- a/src/upgrade.js
+++ b/src/upgrade.js
@@ -967,14 +967,18 @@ Upgrade.upgrade = function(callback) {
 		function(next) {
 			function upgradeHashToSortedSet(hash, callback) {
 				db.getObject(hash, function(err, oldHash) {
-					if (err) {
+					if (err || !oldHash) {
 						return callback(err);
 					}
+
 					db.rename(hash, hash + '_old', function(err) {
 						if (err) {
 							return callback(err);
 						}
 						var keys = Object.keys(oldHash);
+						if (!keys.length) {
+							return callback();
+						}
 						async.each(keys, function(key, next) {
 							db.sortedSetAdd(hash, oldHash[key], key, next);
 						}, callback);