Bug Fix: Update hub.py to fix NoneType error (huggingface#33315)

* Bug Fix: Update hub.py

Bug:
TypeError: argument of type 'NoneType' is not iterable

Analysis:
The error `TypeError: argument of type 'NoneType' is not iterable` suggests that `model_card.data.tags` is `None`, and the code is trying to iterate through it using `not in`.

Fix:

1. **Check if `model_card.data.tags` is `None` before the loop**:
   Since you're checking the variable `tags` before the loop, you should also ensure that `model_card.data.tags` is not `None`. You can do this by initializing `model_card.data.tags` to an empty list if it's `None`.

2. **Updated code**:
   Add a check and initialize the `tags` if it is `None` before proceeding with the iteration.

This way, if `model_card.data.tags` is `None`, it gets converted to an empty list before checking the contents. This prevents the `TypeError`.

* Update hub.py

src/transformers/utils/hub.py

@@ -1198,6 +1198,9 @@ def create_and_tag_model_card(
         model_card = ModelCard.from_template(card_data, model_description=model_description)
 
     if tags is not None:
+        # Ensure model_card.data.tags is a list and not None
+        if model_card.data.tags is None:
+            model_card.data.tags = []
         for model_tag in tags:
             if model_tag not in model_card.data.tags:
                 model_card.data.tags.append(model_tag)