java.lang.NullPointerException
	at org.hl7.fhir.r5.comparison.CodeSystemComparer.findRightProp(CodeSystemComparer.java:321)
	at org.hl7.fhir.r5.comparison.CodeSystemComparer.mergeProps(CodeSystemComparer.java:292)
	at org.hl7.fhir.r5.comparison.CodeSystemComparer.merge(CodeSystemComparer.java:221)
	at org.hl7.fhir.r5.comparison.CodeSystemComparer.compareConcepts(CodeSystemComparer.java:166)
	at org.hl7.fhir.r5.comparison.CodeSystemComparer.compareConcepts(CodeSystemComparer.java:173)
	at org.hl7.fhir.r5.comparison.CodeSystemComparer.compareConcepts(CodeSystemComparer.java:173)
	at org.hl7.fhir.r5.comparison.CodeSystemComparer.compareConcepts(CodeSystemComparer.java:173)
	at org.hl7.fhir.r5.comparison.CodeSystemComparer.compare(CodeSystemComparer.java:124)
	at org.hl7.fhir.r5.comparison.ComparisonSession.compare(ComparisonSession.java:87)
	at org.hl7.fhir.igtools.publisher.comparators.PreviousVersionComparator.finishChecks(PreviousVersionComparator.java:262)
	at org.hl7.fhir.igtools.publisher.Publisher.checkConformanceResources(Publisher.java:4923)
	at org.hl7.fhir.igtools.publisher.Publisher.loadConformance(Publisher.java:4822)
	at org.hl7.fhir.igtools.publisher.Publisher.createIg(Publisher.java:1046)
	at org.hl7.fhir.igtools.publisher.Publisher.execute(Publisher.java:896)
	at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:10401)
	at org.hl7.fhir.igtools.publisher.utils.PublicationProcess.runBuild(PublicationProcess.java:329)
	at org.hl7.fhir.igtools.publisher.utils.PublicationProcess.doPublish(PublicationProcess.java:226)
	at org.hl7.fhir.igtools.publisher.utils.PublicationProcess.publishInner(PublicationProcess.java:175)
	at org.hl7.fhir.igtools.publisher.utils.PublicationProcess.publish(PublicationProcess.java:61)
	at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:10172)