Fixed: Don't repeatedly refresh queue when author deleted

src/NzbDrone.Core/Download/TrackedDownloads/TrackedDownloadService.cs

@@ -56,6 +56,8 @@ namespace NzbDrone.Core.Download.TrackedDownloads
         {
             var updateCacheItems = _cache.Values.Where(x => x.RemoteBook != null && x.RemoteBook.Books.Any(a => a.Id == bookId)).ToList();
 
+            if (updateCacheItems.Any())
+            {
                 foreach (var item in updateCacheItems)
                 {
                     var parsedBookInfo = Parser.Parser.ParseBookTitle(item.DownloadItem.Title);
@@ -69,6 +71,7 @@ namespace NzbDrone.Core.Download.TrackedDownloads
 
                 _eventAggregator.PublishEvent(new TrackedDownloadRefreshedEvent(GetTrackedDownloads()));
             }
+        }
 
         public void StopTracking(string downloadId)
         {