Don't generate a notification for a 0 size SST (#4003)

Summary:
Don't call the OnTableFileCreated listener callback when a 0 size SST
file gets created by Flush. Doing so causes an assertion failure in db_stress. It is also not correct behavior as we call env->DeleteFile() for such files right before the notification.
Closes https://github.com/facebook/rocksdb/pull/4003

Differential Revision: D8461385

Pulled By: anand1976

fbshipit-source-id: ae92d4f921c2e2cff981ad58f4929ed8b609f35d

db/builder.cc

@@ -222,9 +222,11 @@ Status BuildTable(
   }
 
   // Output to event logger and fire events.
+  if (!s.ok() || meta->fd.GetFileSize() > 0) {
     EventHelpers::LogAndNotifyTableFileCreationFinished(
         event_logger, ioptions.listeners, dbname, column_family_name, fname,
         job_id, meta->fd, tp, reason, s);
+  }
 
   return s;
 }