Cannot get rid of light gray border around Sliver body - flutter

Question

Does anyone know why I still have a gray, thin horizontal line at the top and bottom of my body? I'm using SliverAppBar with a SliverFillRemaining below it. I've already set the elevation value of SliverAppBar to be 0.0.
import 'package:flutter/material.dart';
import 'package:curved_navigation_bar/curved_navigation_bar.dart';
class AccountPage extends StatefulWidget {
#override
_AccountPageState createState() => _AccountPageState();
}
class _AccountPageState extends State<AccountPage> {
#override
Widget build(BuildContext context) {
return Scaffold(
backgroundColor: Theme.of(context).primaryColor,
bottomNavigationBar: CurvedNavigationBar(
backgroundColor: Theme.of(context).backgroundColor,
items: <Widget>[
Icon(Icons.add, size: 30),
Icon(Icons.list, size: 30),
Icon(Icons.compare_arrows, size: 30),
],
onTap: (index) {
//Handle button tap
},
),
body: CustomScrollView(
slivers: [
SliverAppBar(
elevation: 0.0,
backgroundColor: Theme.of(context).primaryColor,
expandedHeight: 220.0,
collapsedHeight: 125.0,
pinned: true,
flexibleSpace: Stack(
children: [
Positioned.fill(
child: Image(
image: AssetImage('assets/images/Red_Polygon.jpg'),
fit: BoxFit.cover,
),
),
SafeArea(
child: Column(
mainAxisAlignment: MainAxisAlignment.end,
children: [
Container(
width: double.infinity,
child: Padding(
padding: EdgeInsets.symmetric(
horizontal: 32.0,
vertical: 16.0,
),
child: Column(
mainAxisAlignment: MainAxisAlignment.end,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
Text(
"Hello, \nFIRST_NAME!",
style: TextStyle(
color: Colors.white,
fontSize: 32.0,
),
),
],
),
),
),
Container(
height: 16.0,
width: double.infinity,
decoration: BoxDecoration(
color: Theme.of(context).backgroundColor,
borderRadius: new BorderRadius.only(
topLeft: const Radius.circular(40.0),
topRight: const Radius.circular(40.0),
),
),
),
],
),
),
],
),
),
SliverFillRemaining(
child: Container(
color: Theme.of(context).backgroundColor,
child: Padding(
padding: const EdgeInsets.symmetric(horizontal: 8.0),
child: Column(
children: [
],
),
),
),
),
],
),
);
}
}

Answer 1

make this container to have a decoration color of white
Container(
height: 16.0,
width: double.infinity,
decoration: BoxDecoration(
color:Colors.white,
borderRadius: new BorderRadius.only(
topLeft: const Radius.circular(40.0),
topRight: const Radius.circular(40.0),
),
),
),
for bottom navigation give it a background color of white too.
By default background color is "greyish", you can edit this in Themes