From e22ac9d920b80b577db30c5dc035348e0b91a2e9 Mon Sep 17 00:00:00 2001
From: Jaifroid <egk10@cam.ac.uk>
Date: Sat, 21 Jan 2023 08:33:00 +0000
Subject: [PATCH] Check that SW is actually registered before using for first
 time

---
 www/js/app.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/www/js/app.js b/www/js/app.js
index bfd43d21..346dee26 100644
--- a/www/js/app.js
+++ b/www/js/app.js
@@ -4991,7 +4991,7 @@ define(['jquery', 'zimArchiveLoader', 'uiUtil', 'util', 'utf8', 'cache', 'images
                         return encodeURIComponent(m);
                 });
 
-                if (params.contentInjectionMode === 'serviceworker') {
+                if (params.contentInjectionMode === 'serviceworker' && navigator.serviceWorker.controller) {
                     // Remove page max width restriction if required
                     if (params.removePageMaxWidth) htmlArticle = removePageMaxWidth(htmlArticle);
                     // For UWP apps, we need to add the Zoom level to the HTML if we are opening in external window