java.lang.NullPointerException: Cannot invoke "String.equals(Object)" because the return value of "java.util.Map.get(Object)" is null
	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:86)
	at org.hl7.fhir.igtools.publisher.comparators.PreviousVersionComparator.finishChecks(PreviousVersionComparator.java:256)
	at org.hl7.fhir.igtools.publisher.Publisher.checkConformanceResources(Publisher.java:5153)
	at org.hl7.fhir.igtools.publisher.Publisher.loadConformance(Publisher.java:5020)
	at org.hl7.fhir.igtools.publisher.Publisher.createIg(Publisher.java:1071)
	at org.hl7.fhir.igtools.publisher.Publisher.execute(Publisher.java:902)
	at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:10908)
	at org.hl7.fhir.igtools.web.PublicationProcess.runBuild(PublicationProcess.java:739)
	at org.hl7.fhir.igtools.web.PublicationProcess.doPublish(PublicationProcess.java:393)
	at org.hl7.fhir.igtools.web.PublicationProcess.publishInner(PublicationProcess.java:310)
	at org.hl7.fhir.igtools.web.PublicationProcess.publish(PublicationProcess.java:111)
	at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:10667)