Fixed: Don't process downloads removed from the client

Fixes #3557

src/NzbDrone.Core/Download/DownloadProcessingService.cs

@@ -36,7 +36,9 @@ namespace NzbDrone.Core.Download
         public void Execute(ProcessMonitoredDownloadsCommand message)
         {
             var enableCompletedDownloadHandling = _configService.EnableCompletedDownloadHandling;
-            var trackedDownloads = _trackedDownloadService.GetTrackedDownloads();
+            var trackedDownloads = _trackedDownloadService.GetTrackedDownloads()
+                                                          .Where(t => t.IsTrackable)
+                                                          .ToList();
 
             foreach (var trackedDownload in trackedDownloads)
             {