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:233) 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)