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.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:5106)
	at org.hl7.fhir.igtools.publisher.Publisher.loadConformance(Publisher.java:4975)
	at org.hl7.fhir.igtools.publisher.Publisher.createIg(Publisher.java:1085)
	at org.hl7.fhir.igtools.publisher.Publisher.execute(Publisher.java:914)
	at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:10727)
	at org.hl7.fhir.igtools.publisher.utils.PublicationProcess.runBuild(PublicationProcess.java:330)
	at org.hl7.fhir.igtools.publisher.utils.PublicationProcess.doPublish(PublicationProcess.java:238)
	at org.hl7.fhir.igtools.publisher.utils.PublicationProcess.publishInner(PublicationProcess.java:182)
	at org.hl7.fhir.igtools.publisher.utils.PublicationProcess.publish(PublicationProcess.java:63)
	at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:10490)