diff --git a/lib/providers/my_wallets.dart b/lib/providers/my_wallets.dart
index b48bafb..15101a4 100644
--- a/lib/providers/my_wallets.dart
+++ b/lib/providers/my_wallets.dart
@@ -71,13 +71,13 @@ class MyWalletsProvider with ChangeNotifier {
     return _targetedWallet;
   }
 
-  WalletData? getDefaultWallet([int? chest]) {
+  WalletData getDefaultWallet([int? chest]) {
     if (chestBox.isEmpty) {
       return WalletData(chest: 0, number: 0);
     } else {
       chest ??= getCurrentChest();
       int? defaultWalletNumber = chestBox.get(chest)!.defaultWallet;
-      return getWalletDataById([chest, defaultWalletNumber]);
+      return getWalletDataById([chest, defaultWalletNumber])!;
     }
   }
 
@@ -122,7 +122,7 @@ class MyWalletsProvider with ChangeNotifier {
 
     SubstrateSdk _sub = Provider.of<SubstrateSdk>(context, listen: false);
 
-    WalletData defaultWallet = getDefaultWallet()!;
+    WalletData defaultWallet = getDefaultWallet();
 
     final address = await _sub.derive(
         context, defaultWallet.address!, _newDerivationNbr, pinCode);
@@ -160,7 +160,7 @@ class MyWalletsProvider with ChangeNotifier {
     }
     SubstrateSdk _sub = Provider.of<SubstrateSdk>(context, listen: false);
 
-    WalletData defaultWallet = _myWalletProvider.getDefaultWallet()!;
+    WalletData defaultWallet = _myWalletProvider.getDefaultWallet();
 
     final address =
         await _sub.generateRootKeypair(defaultWallet.address!, pinCode);
diff --git a/lib/screens/myWallets/change_pin.dart b/lib/screens/myWallets/change_pin.dart
index 24c0308..09170ad 100644
--- a/lib/screens/myWallets/change_pin.dart
+++ b/lib/screens/myWallets/change_pin.dart
@@ -105,7 +105,7 @@ class ChangePinScreen extends StatelessWidget with ChangeNotifier {
                   ),
                   onPressed: () async {
                     WalletData defaultWallet =
-                        _myWalletProvider.getDefaultWallet()!;
+                        _myWalletProvider.getDefaultWallet();
 
                     String? _pin;
                     if (_myWalletProvider.pinCode == '') {
diff --git a/lib/screens/myWallets/choose_wallet.dart b/lib/screens/myWallets/choose_wallet.dart
index ab4f790..917f38f 100644
--- a/lib/screens/myWallets/choose_wallet.dart
+++ b/lib/screens/myWallets/choose_wallet.dart
@@ -79,7 +79,7 @@ class ChooseWalletScreen extends StatelessWidget {
     final bool isWalletsExists = _myWalletProvider.checkIfWalletExist();
     WalletData? defaultWallet = _myWalletProvider.getDefaultWallet();
 
-    selectedWallet ??= defaultWallet!;
+    selectedWallet ??= defaultWallet;
     _myWalletProvider.readAllWallets(currentChest);
 
     if (!isWalletsExists) {
diff --git a/lib/screens/myWallets/show_seed.dart b/lib/screens/myWallets/show_seed.dart
index 8d035d8..276caa4 100644
--- a/lib/screens/myWallets/show_seed.dart
+++ b/lib/screens/myWallets/show_seed.dart
@@ -23,14 +23,13 @@ class ShowSeed extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);
-        MyWalletsProvider _myWalletProvider =
+    MyWalletsProvider _myWalletProvider =
         Provider.of<MyWalletsProvider>(context, listen: false);
     CommonElements common = CommonElements();
 
     SubstrateSdk _sub = Provider.of<SubstrateSdk>(context, listen: false);
 
-WalletData defaultWallet =
-                        _myWalletProvider.getDefaultWallet()!;
+    WalletData defaultWallet = _myWalletProvider.getDefaultWallet();
 
     return Scaffold(
         backgroundColor: backgroundColor,
@@ -44,7 +43,8 @@ WalletData defaultWallet =
           child: Column(children: <Widget>[
             const Spacer(flex: 1),
             FutureBuilder(
-                future: _sub.getSeed(defaultWallet.address!, walletProvider.pinCode),
+                future: _sub.getSeed(
+                    defaultWallet.address!, walletProvider.pinCode),
                 builder: (BuildContext context, AsyncSnapshot<String?> _seed) {
                   if (_seed.connectionState != ConnectionState.done ||
                       _seed.hasError) {
@@ -122,7 +122,27 @@ WalletData defaultWallet =
                         ]),
                       ]);
                 }),
-            const Spacer(flex: 3),
+            const Spacer(flex: 2),
+            SizedBox(
+              width: 380 * ratio,
+              height: 60 * ratio,
+              child: ElevatedButton(
+                style: ElevatedButton.styleFrom(
+                  elevation: 4,
+                  primary: orangeC, // background
+                  onPrimary: Colors.white, // foreground
+                ),
+                onPressed: () {
+                  Navigator.pop(context);
+                },
+                child: Text(
+                  'Fermer',
+                  style: TextStyle(
+                      fontSize: 23 * ratio, fontWeight: FontWeight.w600),
+                ),
+              ),
+            ),
+            const Spacer(flex: 2),
           ]),
         ));
   }
diff --git a/lib/screens/myWallets/unlocking_wallet.dart b/lib/screens/myWallets/unlocking_wallet.dart
index 249ce71..540325e 100644
--- a/lib/screens/myWallets/unlocking_wallet.dart
+++ b/lib/screens/myWallets/unlocking_wallet.dart
@@ -219,7 +219,7 @@ class UnlockingWallet extends StatelessWidget {
             onCompleted: (_pin) async {
               _myWalletProvider.pinCode = _pin.toUpperCase();
               final isValid = await _sub.checkPassword(
-                  defaultWallet!.address!, _pin.toUpperCase());
+                  defaultWallet.address!, _pin.toUpperCase());
 
               if (!isValid) {
                 await Future.delayed(const Duration(milliseconds: 50));
diff --git a/lib/screens/myWallets/wallet_options.dart b/lib/screens/myWallets/wallet_options.dart
index 8e2f09d..8a71592 100644
--- a/lib/screens/myWallets/wallet_options.dart
+++ b/lib/screens/myWallets/wallet_options.dart
@@ -354,7 +354,7 @@ class WalletOptions extends StatelessWidget {
       MyWalletsProvider _myWalletProvider,
       WalletOptionsProvider _walletOptions,
       int _currentChest) {
-    WalletData defaultWallet = _myWalletProvider.getDefaultWallet()!;
+    WalletData defaultWallet = _myWalletProvider.getDefaultWallet();
     _walletOptions.isDefaultWallet = (defaultWallet.number == wallet.id()[1]);
 
     return InkWell(
diff --git a/lib/screens/myWallets/wallets_home.dart b/lib/screens/myWallets/wallets_home.dart
index 600da42..14fbc39 100644
--- a/lib/screens/myWallets/wallets_home.dart
+++ b/lib/screens/myWallets/wallets_home.dart
@@ -239,7 +239,7 @@ class WalletsHome extends StatelessWidget {
                                       ),
                           )),
                           balanceBuilder(context, _repository.address!,
-                              _repository.address == defaultWallet!.address),
+                              _repository.address == defaultWallet.address),
                           ListTile(
                             shape: const RoundedRectangleBorder(
                                 borderRadius: BorderRadius.vertical(
diff --git a/lib/screens/transaction_in_progress.dart b/lib/screens/transaction_in_progress.dart
index 502610d..63bfb45 100644
--- a/lib/screens/transaction_in_progress.dart
+++ b/lib/screens/transaction_in_progress.dart
@@ -30,7 +30,7 @@ class TransactionInProgress extends StatelessWidget {
 
     log.d(_walletViewProvider.address!);
 
-    final from = _myWalletProvider.getDefaultWallet()!.name!;
+    final from = _myWalletProvider.getDefaultWallet().name!;
     final to = getShortPubkey(_walletViewProvider.address!);
     final amount = _walletViewProvider.payAmount.text;
     String _actionName = '';
diff --git a/lib/screens/wallet_view.dart b/lib/screens/wallet_view.dart
index 0218d7b..e665aef 100644
--- a/lib/screens/wallet_view.dart
+++ b/lib/screens/wallet_view.dart
@@ -39,7 +39,7 @@ class WalletViewScreen extends StatelessWidget {
     MyWalletsProvider _myWalletProvider =
         Provider.of<MyWalletsProvider>(context, listen: false);
     WalletData? defaultWallet = _myWalletProvider.getDefaultWallet();
-    _sub.setCurrentWallet(defaultWallet!);
+    _sub.setCurrentWallet(defaultWallet);
 
     return Scaffold(
         backgroundColor: backgroundColor,
@@ -108,7 +108,7 @@ class WalletViewScreen extends StatelessWidget {
                 WalletData? _defaultWallet =
                     _myWalletProvider.getDefaultWallet();
                 return FutureBuilder(
-                  future: _sub.isMember(_defaultWallet!.address!),
+                  future: _sub.isMember(_defaultWallet.address!),
                   builder: (context, AsyncSnapshot<bool?> snapshot) {
                     return Visibility(
                       visible: (snapshot.data ?? false),
@@ -282,7 +282,7 @@ class WalletViewScreen extends StatelessWidget {
 
     const double shapeSize = 20;
     WalletData? defaultWallet = _myWalletProvider.getDefaultWallet();
-    log.d(defaultWallet!.address);
+    log.d(defaultWallet.address);
 
     bool canValidate = false;