Coding error when adding/updating a chat with past/current time

If you add/update a mod_chat activity to have the "Next chat time" as the default (current) time or in the past and set repeat/publish to "No repeats - publish the specified time only", on saving, you're presented with a coding exception from a calendar event:

Exception: Coding error detected, it must be fixed by a programmer: The 'timestart' value must be set in other. in ./lib/classes/event/calendar_event_updated.php on line 110.
Stack trace:
line 110 of ./lib/classes/event/calendar_event_updated.php: coding_exception thrown
line 252 of ./lib/classes/event/base.php: call to core\event\calendar_event_updated->validate_data()
line 2365 of ./calendar/lib.php: call to core\event\base::create()
line 653 of ./mod/chat/lib.php: call to calendar_event->update()
line 37 of ./mod/chat/view.php: call to chat_update_chat_times()