minor fixes [skip ci]

lib/src/screens/backup/backup_page.dart

@@ -154,8 +154,12 @@ class BackupPage extends BasePage {
               leftButtonText: S.of(context).share,
               actionRightButton: () async {
                 await backupViewModelBase.saveToDownload(backup.name, backup.file);
-                Navigator.of(dialogContext).pop();
-                await showBar<void>(context, S.of(context).file_saved);
+                if (dialogContext.mounted && Navigator.canPop(dialogContext)) {
+                  Navigator.of(dialogContext).pop();
+                }
+                if (context.mounted && Navigator.canPop(context)) {
+                  await showBar<void>(context, S.of(context).file_saved);
+                }
               },
               actionLeftButton: () async {
                 Navigator.of(dialogContext).pop();

lib/view_model/hardware_wallet/ledger_view_model.dart

@@ -161,7 +161,7 @@ abstract class LedgerViewModelBase extends HardwareWalletViewModel with Store {
             allowChangeWallet: true,
             isReconnect: true,
             onConnectDevice: (context, ledgerVM) async {
-              if (context.mounted) {
+              if (context.mounted && Navigator.of(context).canPop()) {
                 Navigator.of(context).pop();
               }
             },