``` if (validEvents.isEmpty()) validEv...

# codereview

[Eugen Martynov]

if (validEvents.isEmpty())
            validEvents.addAll(FlowOrchestrator.getValidNextEvent(node, messageBody))
        return if (validEvents.isNotEmpty()) {
            validEvents.toObservable().flatMap { notifyNextNode(node, it, messageBody) }
        } else {
            Observable.empty()
        }