add null safety for instance

Author: codehasan

app/src/main/java/io/github/ratul/topactivity/App.java

@@ -38,6 +38,12 @@ public class App extends Application {
     private SharedPreferences sharedPreferences;
     private NotificationManagerCompat notificationManager;
 
+    @Override
+    protected void attachBaseContext(Context base) {
+        super.attachBaseContext(base);
+        instance = this;
+    }
+
     @Override
     public void onCreate() {
         super.onCreate();