Fix ValueError when eval_do_concat_batches=False with examples (#37621)

https://github.com/huggingface/transformers/issues/37593

Co-authored-by: Marc Sun <57196510+SunMarc@users.noreply.github.com>

examples/pytorch/token-classification/run_ner.py

@@ -529,6 +529,9 @@ def main():
 
     def compute_metrics(p):
         predictions, labels = p
+        if not training_args.eval_do_concat_batches:
+            predictions = np.hstack(predictions)
+            labels = np.hstack(labels)
         predictions = np.argmax(predictions, axis=2)
 
         # Remove ignored index (special tokens)