Petals SE Flowable

Unable to find the service task 'xxx' to force its asynchronous execution.

sample-0 2019/06/11 17:40:59,897 GMT+0200 WARNING [org.flowable.engine.common.impl.event.FlowableEventSupport] : Exception while executing event-listener, which was ignored
java.lang.NullPointerException
	at org.ow2.petals.flowable.event.ServiceTaskStartedEventListener.processEvent(ServiceTaskStartedEventListener.java:64)
	at org.ow2.petals.flowable.event.AbstractEventListener.onEvent(AbstractEventListener.java:56)
	at org.flowable.engine.common.impl.event.FlowableEventSupport.dispatchEvent(FlowableEventSupport.java:104)
	at org.flowable.engine.common.impl.event.FlowableEventSupport.dispatchEvent(FlowableEventSupport.java:97)
	at org.flowable.engine.common.impl.event.FlowableEventDispatcherImpl.dispatchEvent(FlowableEventDispatcherImpl.java:65)
	at org.flowable.engine.impl.agenda.ContinueProcessOperation.executeActivityBehavior(ContinueProcessOperation.java:249)
	at org.flowable.engine.impl.agenda.ContinueProcessOperation.executeSynchronous(ContinueProcessOperation.java:154)
	at org.flowable.engine.impl.agenda.ContinueProcessOperation.continueThroughFlowNode(ContinueProcessOperation.java:111)
	at org.flowable.engine.impl.agenda.ContinueProcessOperation.continueThroughSequenceFlow(ContinueProcessOperation.java:303)
	at org.flowable.engine.impl.agenda.ContinueProcessOperation.run(ContinueProcessOperation.java:77)
	at org.flowable.engine.impl.interceptor.CommandInvoker.executeOperation(CommandInvoker.java:88)
	at org.flowable.engine.impl.interceptor.CommandInvoker.executeOperations(CommandInvoker.java:72)
	at org.flowable.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:56)
	at org.flowable.engine.impl.interceptor.BpmnOverrideContextInterceptor.execute(BpmnOverrideContextInterceptor.java:25)
	at org.flowable.engine.common.impl.interceptor.TransactionContextInterceptor.execute(TransactionContextInterceptor.java:53)
	at org.flowable.engine.common.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:72)
	at org.flowable.engine.common.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:30)
	at org.flowable.engine.common.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:56)
	at org.flowable.engine.common.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:51)
	at org.flowable.engine.impl.RuntimeServiceImpl.startProcessInstanceById(RuntimeServiceImpl.java:143)
	at org.ow2.petals.flowable.incoming.operation.NoneStartEventOperation.createProcessInstance(NoneStartEventOperation.java:78)
	at org.ow2.petals.flowable.incoming.operation.StartEventOperation.doExecute(StartEventOperation.java:143)
	at org.ow2.petals.flowable.incoming.operation.FlowableOperation.execute(FlowableOperation.java:211)
	at org.ow2.petals.flowable.incoming.FlowableJBIListener.onJBIMessage(FlowableJBIListener.java:144)
	at org.ow2.petals.component.framework.process.MessageExchangeProcessor.invokeJBIListener(MessageExchangeProcessor.java:525)
	at org.ow2.petals.component.framework.process.MessageExchangeProcessor.processAsProvider(MessageExchangeProcessor.java:493)
	at org.ow2.petals.component.framework.process.MessageExchangeProcessor.process(MessageExchangeProcessor.java:283)
	at org.ow2.petals.component.framework.process.MessageExchangeProcessor.run(MessageExchangeProcessor.java:181)
	at org.ow2.petals.component.framework.process.JBIProcessorThreadPoolExecutor$ExchangeRunnable.run(JBIProcessorThreadPoolExecutor.java:90)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)
	at org.ow2.petals.component.framework.process.JBIProcessorThreadFactory$JBIProcessorThread.run(JBIProcessorThreadFactory.java:99)