Got error when running data_prepro_clean command

[chris-opendata]

Thanks for your great work.
Following the steps, I am up to running the following command for CNNDM datasets,
python data_prepro_clean.py --mode bpe_binarize --input_dir <my_processed-data-dir> --tokenizer_dir <my_bpe-dir>
but got the following error,

Traceback (most recent call last):
File "../fairseq_cli/preprocess.py", line 452, in
cli_main()
File "../fairseq_cli/preprocess.py", line 448, in cli_main
main(args)
File "../fairseq_cli/preprocess.py", line 331, in main
make_all(args.source_lang, src_dict)
File "../fairseq_cli/preprocess.py", line 301, in make_all
make_dataset(vocab, args.trainpref, "train", lang, num_workers=args.workers)
File "../fairseq_cli/preprocess.py", line 297, in make_dataset
make_binary_dataset(vocab, input_prefix, output_prefix, lang, num_workers)
File "../fairseq_cli/preprocess.py", line 173, in make_binary_dataset
100 * sum(replaced.values()) / n_seq_tok[1],
ZeroDivisionError: division by zero

Could you please help? Thanks