Merge branch 'devel' of https://github.com/tinode/webapp into archiving

service-worker.js

@@ -69,6 +69,9 @@ self.addEventListener('notificationclick', function(event) {
 
 // This is needed for 'Add to Home Screen'.
 self.addEventListener('fetch', function(event) {
+    if (event.request.cache === 'only-if-cached' && event.request.mode !== 'same-origin') {
+        return;
+    }
 	event.respondWith(
     //  Try to find response in cache.
     caches.match(event.request)