CAKE-312 | wrapped unlock page by WillPopScope; fixed biometricAuth() in the auth_view_model.dart

lib/router.dart

@@ -237,9 +237,11 @@ Route<dynamic> createRoute(RouteSettings settings) {
     case Routes.unlock:
       return MaterialPageRoute<void>(
           fullscreenDialog: true,
-          builder: (_) => getIt.get<AuthPage>(
-              param1: settings.arguments as OnAuthenticationFinished,
-              param2: false));
+          builder: (_) => WillPopScope(
+              child: getIt.get<AuthPage>(
+                  param1: settings.arguments as OnAuthenticationFinished,
+                  param2: false),
+              onWillPop: () async => false));
 
     case Routes.nodeList:
       return CupertinoPageRoute<void>(

lib/view_model/auth_view_model.dart

@@ -110,8 +110,6 @@ abstract class AuthViewModelBase with Store {
 
         if (isAuthenticated) {
           state = ExecutedSuccessfullyState();
-        } else {
-          state = FailureState('Failure biometric authentication');
         }
       }
     } catch(e) {