gpt2-japanese ERROR when i run fine-tuning code

Question

I have no idea where this error came from, and how to fix it.please help...

the error code when I run

       python3 run_finetune.py --base_model gpt2ja-small --dataset embedded_data_finetune.npz --run_name gpr2ja-finetune

the error is below

      Training...

0
Traceback (most recent call last):
  File "run_finetune.py", line 251, in <module>
    main()
  File "run_finetune.py", line 226, in main
    feed_dict=sample_feature())
  File "run_finetune.py", line 171, in sample_feature
    idx = global_chunk_index[global_chunk_step]
IndexError: index 0 is out of bounds for axis 0 with size 0