Fix example 6 (#572)

lerobot/common/datasets/image_writer.py

@@ -28,7 +28,7 @@ def safe_stop_image_writer(func):
         try:
             return func(*args, **kwargs)
         except Exception as e:
-            dataset = kwargs.get("dataset", None)
+            dataset = kwargs.get("dataset")
             image_writer = getattr(dataset, "image_writer", None) if dataset else None
             if image_writer is not None:
                 print("Waiting for image writer to terminate...")