From 11d058308ff48472aa402697f68ddb4a77658568 Mon Sep 17 00:00:00 2001
From: Amelia <77553571+Fesaa@users.noreply.github.com>
Date: Thu, 19 Jun 2025 11:45:28 +0200
Subject: [PATCH] Fix exception while setting Chapter Ratings when no reviews
 are found fixes #3843

---
 API/Services/Plus/ExternalMetadataService.cs | 29 ++++++++++++--------
 1 file changed, 18 insertions(+), 11 deletions(-)

diff --git a/API/Services/Plus/ExternalMetadataService.cs b/API/Services/Plus/ExternalMetadataService.cs
index 435727bda..35750d7fd 100644
--- a/API/Services/Plus/ExternalMetadataService.cs
+++ b/API/Services/Plus/ExternalMetadataService.cs
@@ -1199,32 +1199,39 @@ public class ExternalMetadataService : IExternalMetadataService
 
         #region Rating
 
-        var averageCriticRating = metadata.CriticReviews.Average(r => r.Rating);
-        var averageUserRating = metadata.UserReviews.Average(r => r.Rating);
+        // C# can't make the implicit conversation here
+        float? averageCriticRating = metadata.CriticReviews.Count > 0 ? metadata.CriticReviews.Average(r => r.Rating) : null;
+        float? averageUserRating = metadata.UserReviews.Count > 0 ? metadata.UserReviews.Average(r => r.Rating) : null;
 
         var existingRatings = await _unitOfWork.ChapterRepository.GetExternalChapterRatings(chapter.Id);
         _unitOfWork.ExternalSeriesMetadataRepository.Remove(existingRatings);
 
-        chapter.ExternalRatings =
-        [
-            new ExternalRating
+        chapter.ExternalRatings = [];
+
+        if (averageUserRating != null)
+        {
+            chapter.ExternalRatings.Add(new ExternalRating
             {
                 AverageScore = (int) averageUserRating,
                 Provider = ScrobbleProvider.Cbr,
                 Authority = RatingAuthority.User,
                 ProviderUrl = metadata.IssueUrl,
-            },
-            new ExternalRating
+
+            });
+            chapter.AverageExternalRating = averageUserRating.Value;
+        }
+
+        if (averageCriticRating != null)
+        {
+            chapter.ExternalRatings.Add(new ExternalRating
             {
                 AverageScore = (int) averageCriticRating,
                 Provider = ScrobbleProvider.Cbr,
                 Authority = RatingAuthority.Critic,
                 ProviderUrl = metadata.IssueUrl,
 
-            },
-        ];
-
-        chapter.AverageExternalRating = averageUserRating;
+            });
+        }
 
         madeModification = averageUserRating > 0f || averageCriticRating > 0f || madeModification;