NPE during shutdown.
Exception in thread "CPS VM execution thread: org.jenkinsci.plugins.workflow.cps.CpsFlowExecution@4e2a2a0c" java.lang.NullPointerException
	at org.jenkinsci.plugins.workflow.cps.nodes.StepStartNode.getDescriptor(StepStartNode.java:36)
	at org.jenkinsci.plugins.workflow.cps.nodes.StepStartNode.getStepName(StepStartNode.java:50)
	at org.jenkinsci.plugins.workflow.cps.nodes.StepEndNode.getTypeDisplayName(StepEndNode.java:37)
	at org.jenkinsci.plugins.workflow.graph.FlowNode.getDisplayName(FlowNode.java:126)
	at org.jenkinsci.plugins.workflow.job.WorkflowRun$GraphL.onNewHead(WorkflowRun.java:574)
	at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution.notifyListeners(CpsFlowExecution.java:594)
	at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$4.run(CpsThreadGroup.java:293)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:744)
Noting CME.
java.lang.RuntimeException: Failed to serialize org.jenkinsci.plugins.workflow.job.WorkflowRun#execution for class org.jenkinsci.plugins.workflow.job.WorkflowRun
	at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:214)
	at hudson.util.RobustReflectionConverter$2.visit(RobustReflectionConverter.java:182)
	at com.thoughtworks.xstream.converters.reflection.PureJavaReflectionProvider.visitSerializableFields(PureJavaReflectionProvider.java:138)
	at hudson.util.RobustReflectionConverter.doMarshal(RobustReflectionConverter.java:167)
	at hudson.util.RobustReflectionConverter.marshal(RobustReflectionConverter.java:108)
	at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:69)
	at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
	at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:43)
	at com.thoughtworks.xstream.core.TreeMarshaller.start(TreeMarshaller.java:82)
	at com.thoughtworks.xstream.core.AbstractTreeMarshallingStrategy.marshal(AbstractTreeMarshallingStrategy.java:37)
	at com.thoughtworks.xstream.XStream.marshal(XStream.java:1026)
	at com.thoughtworks.xstream.XStream.marshal(XStream.java:1015)
	at com.thoughtworks.xstream.XStream.toXML(XStream.java:988)
	at hudson.XmlFile.write(XmlFile.java:178)
	at hudson.model.Run.save(Run.java:1902)
	at org.jenkinsci.plugins.workflow.job.WorkflowRun.copyLogs(WorkflowRun.java:273)
	at org.jenkinsci.plugins.workflow.job.WorkflowRun.waitForCompletion(WorkflowRun.java:216)
	at org.jenkinsci.plugins.workflow.job.WorkflowRun.run(WorkflowRun.java:181)
	at hudson.model.ResourceController.execute(ResourceController.java:88)
	at hudson.model.Executor.run(Executor.java:234)
	at hudson.model.OneOffExecutor.run(OneOffExecutor.java:43)
Caused by: java.util.ConcurrentModificationException
	at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1115)
	at java.util.TreeMap$ValueIterator.next(TreeMap.java:1160)
	at org.jenkinsci.plugins.workflow.cps.CpsFlowExecution$ConverterImpl.marshal(CpsFlowExecution.java:624)
	at hudson.util.XStream2$AssociatedConverterImpl.marshal(XStream2.java:358)
	at com.thoughtworks.xstream.core.AbstractReferenceMarshaller.convert(AbstractReferenceMarshaller.java:69)
	at com.thoughtworks.xstream.core.TreeMarshaller.convertAnother(TreeMarshaller.java:58)
	at com.thoughtworks.xstream.core.AbstractReferenceMarshaller$1.convertAnother(AbstractReferenceMarshaller.java:84)
	at hudson.util.RobustReflectionConverter.marshallField(RobustReflectionConverter.java:223)
	at hudson.util.RobustReflectionConverter$2.writeField(RobustReflectionConverter.java:210)
	... 20 more