The ticket describes what happens on the member's device, where the group isn't meant to be removed, just marked as dissolved. The member calls markGroupDissolved() when handling the creator's leave message.
OK, I need to add events for invitation messages too, so I'll add some code for firing that one at the same time. If you're short of things to do, you could create the event class and write the code for handling it, and I'll write the code for firing it later, or we can do it the other way round if you prefer.