From 17c1a62ec81e78f45c44882a5aba19ef8e7aeb44 Mon Sep 17 00:00:00 2001
From: Akihiko Odaki <akihiko.odaki.4i@stu.hosei.ac.jp>
Date: Wed, 16 May 2018 04:42:31 +0900
Subject: [PATCH] Consider only-if-cached in FetchEvent valid on
 non-Mozilla-Firefox browser (#7506)

---
 app/javascript/mastodon/service_worker/entry.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/app/javascript/mastodon/service_worker/entry.js b/app/javascript/mastodon/service_worker/entry.js
index d28a2be6d..89414f100 100644
--- a/app/javascript/mastodon/service_worker/entry.js
+++ b/app/javascript/mastodon/service_worker/entry.js
@@ -13,7 +13,8 @@ function fetchRoot() {
   return fetch('/', { credentials: 'include' });
 }
 
-const invalidOnlyIfCached = navigator.userAgent.match(/Firefox\/(\d+)/)[1] < 60;
+const firefox = navigator.userAgent.match(/Firefox\/(\d+)/);
+const invalidOnlyIfCached = firefox && firefox[1] < 60;
 
 // Cause a new version of a registered Service Worker to replace an existing one
 // that is already installed, and replace the currently active worker on open pages.