InvalidListenerException when creating multiple Events without method definition.

[calvinalkan]

Assuming the following 2 Listener.

NewAppointment::class => [
			SendStaffBookingConfirmationEmail::class,
			StaffBookingCustomerSync::class,
		],

do not implement __invoke but use the default handleEvent method the ListenerFactory will throw an exception. This happens because for the second listener the "alias" is an integer with value 1. This value needs to be normalized before creating the listener.