Fix web cache and service worker handoff

nginx.conf

@@ -84,6 +84,13 @@ server {
     try_files $uri =404;
   }
 
+  location = /main.dart.js {
+    add_header Cache-Control "no-cache" always;
+    add_header Pragma "no-cache" always;
+    add_header Expires "0" always;
+    try_files /main.dart.js =404;
+  }
+
   location ~* \.(js|mjs|wasm|json|png|jpg|jpeg|gif|webp|svg|ico|woff|woff2|ttf)$ {
     add_header Cache-Control "public, max-age=31536000, immutable" always;
     try_files $uri =404;

web/index.prod.html

@@ -38,8 +38,13 @@
   <script>
     if ('serviceWorker' in navigator) {
       var refreshing = false;
+      var hadServiceWorkerController = !!navigator.serviceWorker.controller;
 
       navigator.serviceWorker.addEventListener('controllerchange', function () {
+        if (!hadServiceWorkerController) {
+          hadServiceWorkerController = true;
+          return;
+        }
         if (refreshing) {
           return;
         }