Fix dataloader cleanup error with no workers (#18732)

Signed-off-by: Mohammed Yasin <32206511+Y-T-G@users.noreply.github.com>

ultralytics/data/build.py

@@ -49,6 +49,7 @@ class InfiniteDataLoader(dataloader.DataLoader):
 
     def __del__(self):
         """Ensure that workers are terminated."""
+        if hasattr(self.iterator, "_workers"):
             for w in self.iterator._workers:  # force terminate
                 if w.is_alive():
                     w.terminate()