Sometimes MUC notifications show list of participants instead of name

Issues
,
1

It seems to be iOS generating this and when it happens the sender is also not shown?

Usually works fine but sometimes this is seen.

2

It seems my sender lookup sometimes produced nil. Based on testing so far I think this fixes it:

	if sender == nil {
		sender = INPerson(
			personHandle: INPersonHandle(value: senderId, type: .unknown),
			nameComponents: nil,
			displayName: senderId,
			image: nil,
			contactIdentifier: nil,
			customIdentifier: nil
		)
	}