From a8a2596228aab7837acb2fee47ffac6598055c6a Mon Sep 17 00:00:00 2001
From: Toby Zerner <toby.zerner@gmail.com>
Date: Mon, 18 May 2015 10:35:12 +0930
Subject: [PATCH] Properly initialise subtree retainers

---
 js/lib/utils/subtree-retainer.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/js/lib/utils/subtree-retainer.js b/js/lib/utils/subtree-retainer.js
index b5430788f..ad82043ca 100644
--- a/js/lib/utils/subtree-retainer.js
+++ b/js/lib/utils/subtree-retainer.js
@@ -13,6 +13,7 @@ export default class SubtreeRetainer {
   constructor() {
     this.invalidate();
     this.callbacks = [].slice.call(arguments);
+    this.old = {};
   }
 
   retain() {
@@ -32,6 +33,6 @@ export default class SubtreeRetainer {
   }
 
   invalidate() {
-    this.old = [];
+    this.old = {};
   }
 }