fix for loading with missing event_id

[drammock]

PR Description

closes #109. There should probably be a test too, but I didn't even see a tests/test_io.py file and at the moment I haven't time to do a proper job of that.

Merge checklist

Maintainer, please confirm the following before merging:

• [ ] All comments resolved
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• [ ] PR title starts with [MRG]
• [x] whats_new.rst is updated
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[drammock]

This CI error: https://github.com/mne-tools/mne-connectivity/actions/runs/3423420815/jobs/5701993749#step:10:54 should have been fixed with matplotlib 3.6.2 (released 7 days ago). It's caused by a change in PySide 6.4, which is quite recent (maybe 1 month old?). I'll push the same fix from https://github.com/mne-tools/mne-python/pull/11246

[drammock]

weird, the updated spec in requirements.txt isn't getting followed? @larsoner any idea what's wrong here?

https://github.com/mne-tools/mne-connectivity/actions/runs/3432799079/jobs/5722434556#step:5:41

[larsoner]

For the 3.7 build I'm guessing there is no fixed wheel, maybe it's 3.8 only? In any case it installs 3.5.something.

I would just bump this build to 3.8. The failures in other builds look legitimate and related like

_________ test_time_resolved_spectral_conn_regression[multitaper-plv] __________
mne_connectivity/spectral/tests/test_spectral.py:590: in test_time_resolved_spectral_conn_regression
    assert_array_almost_equal(conn_data, test_conn)
E   AssertionError: 
E   Arrays are not almost equal to 6 decimals
E   
E   Mismatched elements: 35988 / 36000 (100%)
E   Max absolute difference: 0.02373527
E   Max relative difference: 0.08923911
E    x: array([[[[0.390603, 0.393248, 0.395886, ..., 0.179899, 0.[176](https://github.com/mne-tools/mne-connectivity/actions/runs/3432799079/jobs/5722434609#step:11:177)772,
E             0.173664],
E            [0.24873 , 0.250642, 0.252551, ..., 0.091652, 0.089639,...
E    y: array([[[[0.396488, 0.399161, 0.401826, ..., 0.[179](https://github.com/mne-tools/mne-connectivity/actions/runs/3432799079/jobs/5722434609#step:11:180)551, 0.176434,
E             0.173338],
E            [0.257082, 0.259085, 0.261087, ..., 0.090343, 0.088305,...

[drammock]

For the 3.7 build I'm guessing there is no fixed wheel, maybe it's 3.8 only? In any case it installs 3.5.something.

To me the problem is not the matplotlib version, it's that I specify PySide6!=6.3.0,!=6.4.0 and it installs 6.4.0 anyway.

The failures in other builds look legitimate and related

Legitimate, yes. Related to this PR's changes? I'm not so sure.

[larsoner]

You probably need 6.4.0.1 in the line, too

https://github.com/mne-tools/mne-python/blob/4ef3a88c7c1ea29b4925cece2072ad5c5d826b82/requirements.txt#L12

[adam2392]

Thanks @drammock !