fix null safety

lib/main-dev.dart

@@ -1,3 +1,4 @@
+import 'package:firebase_core/firebase_core.dart';
 import 'package:firebase_messaging/firebase_messaging.dart';
 import 'package:flutter/material.dart';
 import 'package:logging/logging.dart';
@@ -6,8 +7,9 @@ import 'app.dart';
 import 'config.dart';
 import 'data/provider/messaging_fcm.dart';
 
-void main() {
+Future<void> main() async {
   WidgetsFlutterBinding.ensureInitialized();
+  await Firebase.initializeApp();
   FirebaseMessaging.onBackgroundMessage(backgroundMessageHandler);
 
   Config(