fix: Handle missing notification URLs gracefully in the service worker by adding null coalescing and an early exit condition.

public/service-worker.js

@@ -23,7 +23,7 @@ self.addEventListener('push', (event) => {
             vibrate: [200, 100, 200],
             requireInteraction: true,
             data: {
-                url: notification.url
+                url: notification.url || null
             }
         })
     );
@@ -32,17 +32,20 @@ self.addEventListener('push', (event) => {
 self.addEventListener('notificationclick', (event) => {
     event.notification.close();
 
+    const url = event.notification.data && event.notification.data.url;
+
+    if (!url) return;
+
     event.waitUntil(
         clients.matchAll({ type: 'window', includeUncontrolled: true }).then((clientList) => {
-            // Check if there's already a tab open with this URL
             for (const client of clientList) {
-                if (client.url === event.notification.data.url && 'focus' in client) {
+                if (client.url === url && 'focus' in client) {
                     return client.focus();
                 }
             }
             // If not, open a new window
             if (clients.openWindow) {
-                return clients.openWindow(event.notification.data.url);
+                return clients.openWindow(url);
             }
         })
     );