If backend status query has failed due to unknown error code 0, set a delayed retry until success.

ui/app.js

@@ -38,6 +38,8 @@ import * as sshctl from "./control/ssh.js";
 import * as xhr from "./xhr.js";
 import * as cipher from "./crypto.js";
 
+const backendQueryRetryDelay = 2000;
+
 const maxTimeDiff = 30000;
 
 const mainTemplate = `
@@ -204,6 +206,12 @@ function startApp(rootEl) {
               this.page = "auth";
               break;
 
+            case 0:
+              setTimeout(() => {
+                this.tryInitialAuth();
+              }, backendQueryRetryDelay);
+              break;
+
             default:
               alert("Unexpected backend query status: " + result.result);
           }