Crash when using SerafinFile to write a SELAFIN file with no records

Summary

When the HERMES Python API is not available and using SerafinFile instead, a crash occurs when writing a SELAFIN file with no records.

Environment

Operating System: all
TELEMAC version: main

Steps to reproduce

Compile TELEMAC without the HERMES Python API and start vnv_hermes.py from $HOMETEL/examples/python3/TelApy_hermes:

validate_telemac.py vnv_hermes.py

What is the current bug behaviour?

An exception occurs with triforce_no_var.slf.

What is the expected correct behaviour?

It should work flawlessly.

Relevant logs and/or screenshots

Traceback (most recent call last):
  File "/home/user/telemac/examples/python3/TelApy_hermes/test_telemac_file.py", line 200, in <module>
    main()
  File "/home/user/telemac/examples/python3/TelApy_hermes/test_telemac_file.py", line 172, in main
    create_file_from_scratch('triforce_no_var.slf')
  File "/home/user/telemac/examples/python3/TelApy_hermes/test_telemac_file.py", line 61, in create_file_from_scratch
    res.close()
  File "/home/user/telemac/scripts/python3/data_manip/formats/serafin_file.py", line 416, in close
    self.__write()
  File "/home/user/telemac/scripts/python3/data_manip/formats/serafin_file.py", line 377, in __write
    for itime, time in enumerate(self.__times):
                       ^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'NoneType' object is not iterable
Traceback (most recent call last):
  File "/home/user/telemac/scripts/python3/validate_telemac.py", line 827, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/user/telemac/scripts/python3/validate_telemac.py", line 807, in main
    run_validation_python_mpi(cfg, options, report, xcpts)
  File "/home/user/telemac/scripts/python3/validate_telemac.py", line 174, in run_validation_python_mpi
    run_python(py_file, options, report, xcpts)
  File "/home/user/telemac/scripts/python3/validate_telemac.py", line 506, in run_python
    raise exc
  File "/home/user/telemac/scripts/python3/validate_telemac.py", line 473, in run_python
    my_vnv_study.run()
  File "/home/user/telemac/scripts/python3/vvytel/vnv_study.py", line 711, in run
    ret = subprocess.check_call(command['cmd'], shell=True,
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.11/subprocess.py", line 413, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command 'python3 test_telemac_file.py' returned non-zero exit status 1.