IndexError: list index out of range

[firefart]

root@kali:~/xortool# python xortool.py -x input.txt
The most probable key lengths:
Traceback (most recent call last):
  File "xortool.py", line 360, in <module>
    main()
  File "xortool.py", line 40, in main
    update_key_length(ciphertext)
  File "xortool.py", line 95, in update_key_length
    PARAMETERS["known_key_length"] = guess_key_length(text)
  File "xortool.py", line 105, in guess_key_length
    print_fitnesses(fitnesses)
  File "xortool.py", line 140, in print_fitnesses
    best_fitness = top10[0][1]
IndexError: list index out of range

input.txt:

C3601C8A477E

[hellman]

For small files where no bytes repeat - xortool is useles.. Added an error message for case