Fix loading feedback when rating is null

app/lib/feedback/history/feedback_view.dart

@@ -36,7 +36,7 @@ class FeedbackView {
 
   factory FeedbackView.fromUserFeedback(UserFeedback feedback) {
     return FeedbackView(
-      rating: '${feedback.rating}/5.0',
+      rating: feedback.rating == null ? null : '${feedback.rating}/5.0',
       likes: feedback.likes,
       dislikes: feedback.dislikes,
       heardFrom: feedback.heardFrom,

app/lib/feedback/src/models/user_feedback.dart

@@ -77,7 +77,7 @@ class UserFeedback {
   factory UserFeedback.fromJson(Map<String, dynamic> map) {
     return UserFeedback._(
       createdOn: dateTimeFromTimestampOrNull(map['createdOn']),
-      rating: double.tryParse(map['rating']),
+      rating: map['rating'] == null ? null : double.tryParse(map['rating']),
       likes: map['likes'] ?? '',
       dislikes: map['dislikes'] ?? '',
       missing: map['missing'] ?? '',

app/test/feedback/feedback_view_test.dart

@@ -0,0 +1,63 @@
+// Copyright (c) 2022 Sharezone UG (haftungsbeschränkt)
+// Licensed under the EUPL-1.2-or-later.
+//
+// You may obtain a copy of the Licence at:
+// https://joinup.ec.europa.eu/software/page/eupl
+//
+// SPDX-License-Identifier: EUPL-1.2
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:sharezone/feedback/history/feedback_view.dart';
+import 'package:sharezone/feedback/src/models/user_feedback.dart';
+
+void main() {
+  group(FeedbackView, () {
+    test('.fromUserFeedback() empty', () {
+      final feedback = UserFeedback.create();
+      final view = FeedbackView.fromUserFeedback(feedback);
+
+      expect(view.rating, isNull);
+      expect(view.likes, '');
+      expect(view.dislikes, '');
+      expect(view.heardFrom, '');
+      expect(view.missing, '');
+      expect(view.createdOn, isNull);
+    });
+
+    test('.fromUserFeedback() with data', () {
+      final feedback = UserFeedback.create().copyWith(
+        rating: 5.0,
+        dislikes: 'd',
+        heardFrom: 'h',
+        likes: 'l',
+        missing: 'm',
+      );
+      final view = FeedbackView.fromUserFeedback(feedback);
+
+      expect(view.rating, '5.0/5.0');
+      expect(view.likes, 'l');
+      expect(view.dislikes, 'd');
+      expect(view.heardFrom, 'h');
+      expect(view.missing, 'm');
+      expect(view.createdOn, isNull);
+    });
+
+    test('.hasX returns null even it is empty', () {
+      const view = FeedbackView(
+        createdOn: '',
+        rating: '',
+        likes: '',
+        dislikes: '',
+        heardFrom: '',
+        missing: '',
+      );
+
+      expect(view.hasCreatedOn, isFalse);
+      expect(view.hasRating, isFalse);
+      expect(view.hasLikes, isFalse);
+      expect(view.hasDislikes, isFalse);
+      expect(view.hasHeardFrom, isFalse);
+      expect(view.hasMissing, isFalse);
+    });
+  });
+}