Whenever App is restarted hive database gets cleared

**Question**
Whenever I restart my app hive database gets cleared & show null check error, but if i close the app in background it works properly.

**Code sample**
```dart
await Hive.initFlutter();
Hive.registerAdapter(ProgressListAdapter());
Hive.registerAdapter(VideoListAdapter());
Hive.registerAdapter(DashBoardAdapter());
Hive.registerAdapter(CourseDetailsAdapter());
Hive.registerAdapter(AnnouncementsListDataAdapter());
Hive.registerAdapter(VideoAssignmentsAdapter());
Hive.registerAdapter(LessonDetailAdapter());
Hive.registerAdapter(CourseQuestionsAdapter());
await Hive.openBox("box");
await Hive.openBox("video_box");
await Hive.openBox("dashboard_box");
await Hive.openBox("course_box");
await Hive.openBox("announcement_box");
await Hive.openBox("vfs_feedback_box");
await Hive.openBox("lesson_box");
await Hive.openBox("questions_box");
await Hive.openBox("video_record_box");
```

**Version**
- Platform: iOS, Android, Mac, Windows, Linux, Web
- Flutter version: [3.0.2]
- Hive version: [2.2.3]

Start by reproducing the difference between restarting the app and closing it in the background using the shown Hive.initFlutter and Hive.openBox calls. Check whether the opened boxes retain their data after a full restart and identify why the null check error occurs. Done means the stored data remains available and the error no longer appears after restarting.

Written by the indexing model from the issue text.