FIX: Avoid iteration errors caused by None when reading Nihon Kohden .LOG files

[myd7349]

Reference issue (if any)

Reported by @eulerleibniz .

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Hello there @larsoner . Not sure if i need to create a new issue for this, but the new code has a bug here:
in line 341 here:

            for li, t_log in enumerate(t_logs): # Chek if t_logs Is None
                t_desc, t_onset = _parse_event_log(t_log)
                if t_sub_logs is not None and t_sub_logs.size == t_logs.size:
                    t_sub_desc, t_sub_onset = _parse_sub_event_log(t_sub_logs[li])
                    t_desc += t_sub_desc
                    t_onset += t_sub_onset

You did not check if t_logs is None, so we get errors on enumerate.

Originally posted by @eulerleibniz in #13251 (comment)

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@myd7349 I just did what you asked. using mne.version = 1.12.1

The error doesn't happen with my files which have EEG-1100A V01.00 in their header.
It only happens with EEG files which have header EEG-1200A V01.00.
I also checked the mne version=1.10.0 of the mne which also had issues with this old format and they clearly wrote this in nihon file in line 50:

_valid_headers = [
    "EEG-1100A V01.00",
    "EEG-1100B V01.00",
    "EEG-1100C V01.00",
    "QI-403A   V01.00",
    "QI-403A   V02.00",
    "EEG-2100  V01.00",
    "EEG-2100  V02.00",
    "DAE-2100D V01.30",
    "DAE-2100D V02.00",
    # 'EEG-1200A V01.00',  # Not working for the moment.
]

where it was clearly mentioned that they don't support that specific version yet.
here is the output of the prints you asked on these files:

🪲 Failed to read version: [''], expected: EEG-1200A V01.00.
🪲 Failed to read version: [''], expected: EEG-1200A V01.00.
Traceback (most recent call last):
  File "c:\GitHub\Vigilant\vigilant\emu\sop_v0_1_0\nihon.py", line 460, in <module>
    raw_mne = mne.io.read_raw_nihon(path, preload=False)
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Titania\anaconda3\envs\devenv\Lib\site-packages\mne\io\nihon\nihon.py", line 52, in read_raw_nihon
    return RawNihon(fname, preload, encoding=encoding, verbose=verbose)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<decorator-gen-207>", line 12, in __init__
  File "C:\Users\Titania\anaconda3\envs\devenv\Lib\site-packages\mne\io\nihon\nihon.py", line 506, in __init__
    annots = _read_nihon_annotations(fname, encoding)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\Titania\anaconda3\envs\devenv\Lib\site-packages\mne\io\nihon\nihon.py", line 375, in _read_nihon_annotations
    for li, t_log in enumerate(t_logs):
                     ^^^^^^^^^^^^^^^^^
TypeError: 'NoneType' object is not iterable

Originally posted by @eulerleibniz in #13251 (comment)

What does this implement/fix?

This is a follow-up to #13251. In #13251, some additional checks were added to _read_event_log_block (including a version check), which could cause _read_event_log_block to return None, leading to iteration errors.

This change avoids that issue by returning an empty array instead of None when reading fails. In addition, when the version does not match, a warning is now issued instead of returning None.

Additional information

[larsoner]

Seems reasonable to me! I'll commit the suggested change and mark for merge-when-green, thanks in advance @myd7349 !