Why do I get this line between Containers? - flutter

Question

Why do I get a line the color of the image on the bottom of the stack between Containers x and y? And what can I do to avoid that line?print of the screen
I want to have a Container with the standard background color and another one that has the fade effect and both these Containers are supposed to be on top of the background Image
#override
Widget build(BuildContext context) {
FluxoPermissaoNotificacoes fluxo = ModalRoute.of(context)!.settings.arguments as FluxoPermissaoNotificacoes;
DataPermissaoNotificacoes data = getDataPermissaoNotificacoes(fluxo);
return Scaffold(body: Container(
height: MediaQuery.of(context).size.height,
child: Stack(children: [
Stack(
children: [
Padding(padding: EdgeInsets.only(top: 38, left: 0),
child: Container(child: Image.asset("assets/images/permissao_notificacoes.png")),
),
Positioned(top: MediaQuery.of(context).size.height * 0.3, child: SizedBox(
width: MediaQuery.of(context).size.width,
child: Padding(
padding: const EdgeInsets.symmetric(horizontal: 46.0),
child: Container(decoration: BoxDecoration(borderRadius: BorderRadius.all(Radius.circular(13)),
color: Color(0xffEBEBEB)), child: Padding(
padding: const EdgeInsets.all(8.0),
child: Column(crossAxisAlignment: CrossAxisAlignment.start, children: [
Row(children: [
ClipRRect(borderRadius: BorderRadius.all(Radius.circular(5)), child: Image.asset(F.logoSquare ?? 'assets/applogo/android_logo_acad.png', width: 17,)),
Padding(
padding: const EdgeInsets.only(left: 5.0),
child: Text(F.nomeApp, style: TextStyle(fontFamily: 'SFCompact', color: Colors.black, fontSize: 12, fontWeight: FontWeight.w500)),
),
],),
SizedBox(height: 8,),
Text('A sua próxima aula irá começar em meia hora', style: TextStyle(fontFamily: 'SFCompact', color: Colors.black, fontSize: 12, fontWeight: FontWeight.w400))
],),
),),
),
)),
],
),
Column(mainAxisAlignment: MainAxisAlignment.end,
children: [
//container x
Container(height: MediaQuery.of(context).size.height * 0.29,
decoration: BoxDecoration(
gradient: LinearGradient(
end: Alignment.bottomCenter,
begin: Alignment.topCenter,
colors: GetIt.I.get<ControladorApp>().themeMode == ThemeMode.dark ? [
Colors.black.withOpacity(0.0),
Colors.black.withOpacity(0.2),
Colors.black.withOpacity(0.4),
Colors.black.withOpacity(0.6),
Colors.black.withOpacity(0.8),
Colors.black.withOpacity(1),
Colors.black.withOpacity(1),
] : [
Color(0xffFAFAFA).withOpacity(0.0),
Color(0xffFAFAFA).withOpacity(0.1),
Color(0xffFAFAFA).withOpacity(0.25),
Color(0xffFAFAFA).withOpacity(0.5),
Color(0xffFAFAFA).withOpacity(0.8),
Color(0xffFAFAFA),
Color(0xffFAFAFA),
],
),
),
),
//container y
Container(
color: Theme.of(context).backgroundColor,
child: Column(
children: [
SizedBox(height: 12,),
TextHeader(data.headText, textAlign: TextAlign.center,),
SizedBox(height: 16,),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 24.0),
child: TextBody1(data.bodyText, textAlign: TextAlign.center,),
),
SizedBox(height: 24,),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 16.0),
child: BotaoPrimario(onTap: () {}, value: "Permitir Notificações",),
),
SizedBox(height: 8,),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 16.0),
child: BotaoPrimario(onTap: () {
_controladorNotificacao.onTapAgoraNao();
}, value: "Agora não", bordered: true, textColor: Theme.of(context).primaryColor, corDefault: Theme.of(context).cardColor),
),
SizedBox(height: 32,),
],
),
),
],
)
],
),
));
}