java.lang.Error: What?
	at org.hl7.fhir.r5.utils.DefinitionNavigator.loadChildren(DefinitionNavigator.java:287)
	at org.hl7.fhir.r5.utils.DefinitionNavigator.isChildrenFromReference(DefinitionNavigator.java:486)
	at org.hl7.fhir.r5.comparison.StructureDefinitionComparer.compareChildren(StructureDefinitionComparer.java:353)
	at org.hl7.fhir.r5.comparison.StructureDefinitionComparer.compareElements(StructureDefinitionComparer.java:286)
	at org.hl7.fhir.r5.comparison.StructureDefinitionComparer.compareChildren(StructureDefinitionComparer.java:377)
	at org.hl7.fhir.r5.comparison.StructureDefinitionComparer.compareElements(StructureDefinitionComparer.java:286)
	at org.hl7.fhir.r5.comparison.StructureDefinitionComparer.compareChildren(StructureDefinitionComparer.java:377)
	at org.hl7.fhir.r5.comparison.StructureDefinitionComparer.compareElements(StructureDefinitionComparer.java:286)
	at org.hl7.fhir.r5.comparison.StructureDefinitionComparer.compare(StructureDefinitionComparer.java:164)
	at org.hl7.fhir.r5.comparison.ComparisonSession.compare(ComparisonSession.java:107)
	at org.hl7.fhir.igtools.publisher.comparators.PreviousVersionComparator.finishChecks(PreviousVersionComparator.java:267)
	at org.hl7.fhir.igtools.publisher.PublisherProcessor.checkConformanceResources(PublisherProcessor.java:1496)
	at org.hl7.fhir.igtools.publisher.PublisherProcessor.loadConformance2(PublisherProcessor.java:104)
	at org.hl7.fhir.igtools.publisher.Publisher.createIg(Publisher.java:404)
	at org.hl7.fhir.igtools.publisher.Publisher.execute(Publisher.java:233)
	at org.hl7.fhir.igtools.publisher.Publisher.main(Publisher.java:1600)