From 323d8d5d674e6ce17542e349a6dcf4ead5372e5f Mon Sep 17 00:00:00 2001
From: Tim Nguyen <nt1m@users.noreply.github.com>
Date: Tue, 1 May 2018 03:39:10 +0100
Subject: [PATCH] Return early if browser.theme.onUpdated is undefined (#344)

---
 src/sidebar/tabcenter.js | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/sidebar/tabcenter.js b/src/sidebar/tabcenter.js
index 9a07a82..e1498e1 100644
--- a/src/sidebar/tabcenter.js
+++ b/src/sidebar/tabcenter.js
@@ -75,6 +75,9 @@ TabCenter.prototype = {
     }
   },
   set _themeIntegration(enabled) {
+    if (!browser.theme.onUpdated) {
+      return;
+    }
     if (!enabled) {
       this._resetTheme();
       if (browser.theme.onUpdated.hasListener(this._themeListener)) {