fix(firebase): add null checks for service worker registration and token

- Add guard clause in useNotificationToken to skip setting state if token is empty
- Add check for navigator.serviceWorker support in initServiceWorker
- Handle service worker registration failure in getFirebaseToken by returning empty string
- Prevents errors and invalid states when Service Worker is unsupported or fails to initialize

src/hooks/useNotificationToken.ts

@@ -8,6 +8,7 @@ export const useNotificationToken = () => {
     if (!isNotificationSupport()) return;
     getFirebaseToken()
       .then(token => {
+        if (!token) return;
         setToken(token);
       })
       .catch(() => {});

src/utils/firebase-frontend.ts

@@ -20,9 +20,9 @@ export const getFirebaseApp = () => {
   }
   return firebase.app;
 };
-// getAnalytics(app);
 
 export const initServiceWorker = async () => {
+  if (!navigator.serviceWorker) return;
   if (!firebase.registeration) {
     firebase.registeration = await navigator.serviceWorker.register('/sw.js', {
       scope: '/',
@@ -41,6 +41,7 @@ export const getFirebaseMessaging = () => {
 
 export async function getFirebaseToken() {
   const registeration = await initServiceWorker(); 
+  if (!registeration) return '';
   await registeration.update();
   const token = await getToken(getFirebaseMessaging(), { 
     vapidKey: VAPI_PUBLIC_KEY,