p-values of 0 cause error in cross_corr_matrix()

[tleonardi]

  File "/usr/local/bin/nanocompore", line 9, in <module>
    load_entry_point('nanocompore==1.0.0rc1', 'console_scripts', 'nanocompore')()
  File "/usr/local/lib/python3.5/dist-packages/nanocompore/nanocompore_main.py", line 142, in main
    args.func(args)
  File "/usr/local/lib/python3.5/dist-packages/nanocompore/nanocompore_main.py", line 177, in sampcomp_main
    db = s()
  File "/usr/local/lib/python3.5/dist-packages/nanocompore/SampComp.py", line 253, in __call__
    raise E
  File "/usr/local/lib/python3.5/dist-packages/nanocompore/SampComp.py", line 245, in __call__
    raise NanocomporeError(tb)
nanocompore.common.NanocomporeError: Traceback (most recent call last):
  File "/usr/local/lib/python3.5/dist-packages/nanocompore/SampComp.py", line 368, in __process_references
    random_state=random_state)
  File "/usr/local/lib/python3.5/dist-packages/nanocompore/TxComp.py", line 114, in txCompare
    corr_matrix_dict[test] = cross_corr_matrix(pval_list_dict[test], sequence_context)
  File "/usr/local/lib/python3.5/dist-packages/nanocompore/TxComp.py", line 333, in cross_corr_matrix
    raise NanocomporeError("At least one p-value is invalid")
nanocompore.common.NanocomporeError: At least one p-value is invalid