From b9fbe1211887219ecfdcce4fb933e3aed393f718 Mon Sep 17 00:00:00 2001
From: Jermolene <jeremy@jermolene.com>
Date: Fri, 17 Mar 2017 14:20:04 +0000
Subject: [PATCH] More defensive deepFreeze()

IE11 chokes on Object.freeze(undefined)
---
 core/modules/utils/utils.js | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/core/modules/utils/utils.js b/core/modules/utils/utils.js
index 3c4736ddf..bc32711e3 100644
--- a/core/modules/utils/utils.js
+++ b/core/modules/utils/utils.js
@@ -224,11 +224,13 @@ exports.extendDeepCopy = function(object,extendedProperties) {
 
 exports.deepFreeze = function deepFreeze(object) {
 	var property, key;
-	Object.freeze(object);
-	for(key in object) {
-		property = object[key];
-		if($tw.utils.hop(object,key) && (typeof property === "object") && !Object.isFrozen(property)) {
-			deepFreeze(property);
+	if(object) {
+		Object.freeze(object);
+		for(key in object) {
+			property = object[key];
+			if($tw.utils.hop(object,key) && (typeof property === "object") && !Object.isFrozen(property)) {
+				deepFreeze(property);
+			}
 		}
 	}
 };