Fixed: Don't delete down indexers if they still exist in DB

Fixes #494

src/NzbDrone.Core/Applications/ApplicationService.cs

@@ -159,9 +159,11 @@ namespace NzbDrone.Core.Applications
 
                 if (removeRemote)
                 {
+                    var allIndexers = _indexerFactory.All();
+
                     foreach (var mapping in indexerMappings)
                     {
-                        if (!indexers.Any(x => x.Id == mapping.IndexerId))
+                        if (!allIndexers.Any(x => x.Id == mapping.IndexerId))
                         {
                             _logger.Info("Indexer with the ID {0} was found within {1} but is no longer defined within Prowlarr, this is being removed.", mapping.IndexerId, app.Name);
                             ExecuteAction(a => a.RemoveIndexer(mapping.IndexerId), app);