tabulate_behavior_data() needs a way to handle data missing ecube

Sometimes, experiment data is missing the related ecube data (not sure if it exists somewhere and didn't get linked by the database, or didn't get saved at all). Example of this is beignet on 12-29-2022, id = 7843:


`tabulate_behavior_data()` will break when it tries to use event timestamps to segment trials, because these timestamps won't exist for such experiments.