🐛 Trying to fix sync API of messages

DysonNetwork.Sphere/Chat/ChatService.cs

@@ -341,13 +341,13 @@ public partial class ChatService(
                 m => m!.ChatRoomId,
                 m => m
             );
-        
+
         var messageSenders = messages
             .Select(m => m.Value!.Sender)
             .DistinctBy(x => x.Id)
             .ToList();
         messageSenders = await crs.LoadMemberAccounts(messageSenders);
-        
+
         foreach (var message in messages)
             message.Value!.Sender = messageSenders.First(x => x.Id == message.Value.SenderId);
 
@@ -470,6 +470,7 @@ public partial class ChatService(
             .ToListAsync();
 
         var changesMembers = changes
+            .Where(c => c.Message != null)
             .Select(c => c.Message!.Sender)
             .DistinctBy(x => x.Id)
             .ToList();
@@ -595,4 +596,4 @@ public class SyncResponse
 {
     public List<MessageChange> Changes { get; set; } = [];
     public Instant CurrentTimestamp { get; set; }
-}
+}