From 072960f5c3d193dc61ce85d39bbdc0fd18a2256f Mon Sep 17 00:00:00 2001
From: Denis Declara <declara91@gmail.com>
Date: Wed, 29 Mar 2017 17:26:57 +0200
Subject: [PATCH] Added nullptr guard to avoid exceptions

---
 src/subscribables/observableArray.changeTracking.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/subscribables/observableArray.changeTracking.js b/src/subscribables/observableArray.changeTracking.js
index 563f48066..66c5fad18 100644
--- a/src/subscribables/observableArray.changeTracking.js
+++ b/src/subscribables/observableArray.changeTracking.js
@@ -36,7 +36,8 @@ ko.extenders['trackArrayChanges'] = function(target, options) {
                 target['notifySubscribers'] = underlyingNotifySubscribersFunction;
                 underlyingNotifySubscribersFunction = undefined;
             }
-            arrayChangeSubscription.dispose();
+            if (arrayChangeSubscription)
+	        arrayChangeSubscription.dispose();
             arrayChangeSubscription = null;
             trackingChanges = false;
         }