#284 - Allow registration of classes without any subscriptions

[Dominiquini]

Add EventBusBuilder.throwNoSubscribersException(boolean throwNoSubscribersException) to allow objects to register in the EventBus without subscribing to any event.

This allows, for example, to register on a base class, without having to replicate the registering logic in all sub-classes.

This implements the feature requested at #284.

[renaudcerrato]

+1

[rakshith-ravi]

What's the status on this? Any updates? Would really like to see this in the next release. @greenrobot-team @Dominiquini