The getter 'activePageIndex' was called on null. Receiver: null Tried calling: activePageIndex) - flutter

Question

while creating a liquid swipe with smooth page indicator I am getting an error
the error which I getting is
NoSuchMethodError (NoSuchMethodError: The getter 'activePageIndex' was called on null. Receiver: nullTried calling: activePageIndex)
Please anyone can help me to get rid of this error
My Code
import 'package:flutter/material.dart';
import 'package:liquid_swipe/liquid_swipe.dart';
import 'package:smooth_page_indicator/smooth_page_indicator.dart';
void main(List<String> args) {
runApp(MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
home: SwipeHome(),
);
}
}
class SwipeHome extends StatefulWidget {
#override
State<SwipeHome> createState() => _SwipeHomeState();
}
class _SwipeHomeState extends State<SwipeHome> {
final controller= LiquidController();
#override
Widget build(BuildContext context) {
return Scaffold(
body: Stack(
children :[
LiquidSwipe(
liquidController: controller,
enableSlideIcon: true,
onPageChangeCallback: (index){
setState(() {
});
},
slideIconWidget: Icon(Icons.arrow_back_ios_new,color: Colors.white,),
pages:[
BuildPage(color: Color.fromARGB(255, 27, 4, 119),
urlImage: "https://i.pcmag.com/imagery/articles/04HUXgEu0I3mdCOejOjQpNE-5.fit_lim.size_1600x900.v1620748900.jpg",
title: "Facebook",
subtitle: "nfvfhgsdcfyfshsiufifuihgiugerbdfyfu"),
BuildPage(color: Colors.white,
urlImage: "https://images.unsplash.com/photo-1636751364472-12bfad09b451?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=870&q=80",
title: "Whatsapp",
subtitle: "nfvfhgsdcfyfshsiufifuihgiugerbdfyfu"),
BuildPage(color: Colors.orange,
urlImage: "https://akm-img-a-in.tosshub.com/indiatoday/images/story/202108/Instagram_0.jpg?ZZLGdE1PjohTO.aeUOUEQYBxAWLPgCGT&size=770:433",
title: "Instagram",
subtitle: "nfvfhgsdcfyfshsiufifuihgiugerbdfyfu")
]),
Positioned(
bottom: 0,
left: 16,
right: 32,
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: [
TextButton(onPressed: (){
controller.animateToPage(page: 2);
}, child: Text("Skip",style: TextStyle(color: Colors.white,fontSize: 15),)),
AnimatedSmoothIndicator(activeIndex:controller.currentPage,//THIS IS WHERE I AM GETTING ERROR//
count: 3,
effect: JumpingDotEffect(),
onDotClicked: (index){
controller.animateToPage(page: index);
},
),
TextButton(onPressed: (){
final page = controller.currentPage+1;
controller.animateToPage(page: page>3?0:page,duration: 300);
}, child: Text("Next",style: TextStyle(color: Colors.white,fontSize: 15),)),
],
))
]
)
);
}
Widget BuildPage({required Color color,
required String urlImage,
required String title,
required String subtitle,
}){
return Container(
color: color,
padding: EdgeInsets.symmetric(horizontal: 24),
child: Column(
crossAxisAlignment: CrossAxisAlignment.start,
mainAxisAlignment: MainAxisAlignment.center,
children: [
Image.network(urlImage,fit: BoxFit.cover,
width: double.infinity,),
SizedBox(height: 64),
Center(child: Text(title,style: TextStyle(color: Colors.white,fontSize: 28,fontWeight: FontWeight.bold),)),
SizedBox(height: 24),
Container(
child: Text(subtitle,style:TextStyle(color: Colors.white,fontSize: 20,)),
)
],
),
);
}
}
*Plz anyone can help me to get rid of this error