[modelcard] Set model name if empty (#20496)

* [modelcard] Set model name if empty

* no magic
Co-authored-by: Sylvain Gugger <sylvain@huggingface.co>
Co-authored-by: Sylvain Gugger <sylvain@huggingface.co>

src/transformers/modelcard.py

@@ -591,6 +591,8 @@ class TrainingSummary:
 
         if model_name is None:
             model_name = Path(trainer.args.output_dir).name
+        if len(model_name) == 0:
+            model_name = finetuned_from
 
         # Add `generated_from_trainer` to the tags
         if tags is None: