Sorry for that. Would you prefer a new MR or a new issue ticket?
Thank you for doing the code cleanup. I've created patches but this was my first MR.
It all looks good to me. I just made a couple of minor changes to the comments in the code to reflect the refactoring.
esomething → created an issue.
I think that the issue happens on rows in the view results for which there are no scheduled transitions. The value for the scheduled transition fields (new state, previous state and revision link) are empty, and the errors happen when Drupal, trying to render these fields, attempts to execute methods on these null values.
I've added a simple check for null values. It works for me.
I noticed that the code in ScheduledTransitionFromStateViewsField.php is quite different from ScheduledTransitionToStateViewsField.php. I don't understand the reason for this. Perhaps the module's maintainer will know.