Flutter Drawer is not visible and the page gives error - flutter

Question

Hi I'm routing menu with Drawer. It works fine for 2 pages but there is one page gives error.
The menu works correctly when I first press it, then when I go to another page and come back it gives this error
Also I tryed routing with routes on mainApp buut this way seemed easier to me
My drawer
class MyDrawer extends StatefulWidget {
#override
State<StatefulWidget> createState() => _MyDrawerState();
}
class _MyDrawerState extends State {
#override
Widget build(BuildContext context) {
return Drawer(
child: ListView(
children: <Widget>[
DrawerHeader(
child: Align(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
"Test",
style: TextStyle(color: Colors.white, fontSize: 25.0),
),
],
),
),
decoration: BoxDecoration(
color: Colors.blue,
),
),
ListTile(
leading: Icon(Icons.home),
title: Text('Main'),
trailing: Icon(Icons.arrow_right),
onTap: () {
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => Main(),
));
},
),
ListTile(
leading: Icon(Icons.perm_device_information),
title: Text('How'),
trailing: Icon(Icons.arrow_right),
onTap: () {
//Navigator.pushNamed(context, "/how");
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => HowItWorks(),
));
},
),
ListTile(
leading: Icon(Icons.keyboard),
title: Text('Contact'),
trailing: Icon(Icons.arrow_right),
onTap: () {
//Navigator.pushNamed(context, "/contact");
Navigator.push(
context,
MaterialPageRoute(
builder: (context) => SendMail(),
));
},
),
],
),
);
}
}
this is the page it gives error on second route and drawer is not visible
final _formKey2 = GlobalKey<FormState>();
class SendMail extends StatelessWidget {
#override
Widget build(BuildContext context) {
return Scaffold(
drawer: MyDrawer(),
body: Center(
child: Form(
key: _formKey2,
child: Padding(
padding: const EdgeInsets.all(18.0),
child: Column(
crossAxisAlignment: CrossAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.all(48.0),
child: Text(
'İletişim',
style: TextStyle(fontWeight: FontWeight.bold),
),
),
Text('Contact Me'),
Padding(
padding: const EdgeInsets.symmetric(horizontal: 16.0),
child: Column(
children: <Widget>[
Padding(
padding: const EdgeInsets.all(8.0),
child: TextFormField(
keyboardType: TextInputType.text,
validator: (value) {
if (value.isEmpty) {
return 'Can not be empty';
}
return null;
},
decoration: InputDecoration(
filled: true,
hintText: 'Name',
border: InputBorder.none),
),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: TextFormField(
keyboardType: TextInputType.emailAddress,
decoration: InputDecoration(
filled: true,
hintText: 'Email',
border: InputBorder.none),
),
),
Padding(
padding: const EdgeInsets.all(8.0),
child: TextFormField(
maxLines: 7,
validator: (value) {
if (value.isEmpty) {
return 'Can not be empty';
}
return null;
},
decoration: InputDecoration(
filled: true,
hintText: 'Message',
border: InputBorder.none),
),
),
],
),
)
],
),
Detailed error