Media annotations are sometimes created without target.selector
In the DSHS version students have issues with a specific timeline that does not load. The error is "Unknown datetime argument: null, of type object". The error only shows up as an error message in the UI but not in console output. No content is displayed in the timeline viewer although there should be something on the timeline (reported by students and indicated by a timeline preview image).
I can't reproduce the issue with any other timeline.
@anton.koch: I could provide the ID of the timeline, if required