From c06be58a33b06e721210d29c40f14224a85aa24d Mon Sep 17 00:00:00 2001
From: Andrey <andrey-git@users.noreply.github.com>
Date: Mon, 8 Jan 2018 00:13:49 +0200
Subject: [PATCH] Fix possible JS error (#789)

---
 src/components/state-history-charts.html | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/components/state-history-charts.html b/src/components/state-history-charts.html
index 04cf753fb1..f827adef88 100644
--- a/src/components/state-history-charts.html
+++ b/src/components/state-history-charts.html
@@ -116,8 +116,8 @@ class StateHistoryCharts extends Polymer.Element {
   }
 
   _computeIsEmpty(historyData) {
-    return (historyData &&
-            historyData.timeline.length === 0 &&
+    return !historyData || !historyData.timeline || !historyData.line ||
+           (historyData.timeline.length === 0 &&
             historyData.line.length === 0);
   }