Fix NPE in CompatibilityUpgrader

This happens when there is an anonomous element referenced in a package
relationship.

Note that this should not happen in a valid SPDX documents since all
elements must have SPDXRef- ID's which will generate a URI reference.

Signed-off-by: Gary O'Neall <gary@sourceauditor.com>

Author: goneall

src/main/java/org/spdx/spdxRdfStore/CompatibilityUpgrader.java

@@ -132,7 +132,7 @@ private static void upgradeHasFiles(Model model, String documentNamespace) {
 	            	Resource existingRelationship = stmt.getObject().asResource();
 	            	Resource relatedElement = existingRelationship.getPropertyResourceValue(model.createProperty(SpdxConstants.SPDX_NAMESPACE + SpdxConstants.PROP_RELATED_SPDX_ELEMENT));
 	            	Resource relationshipType = existingRelationship.getPropertyResourceValue(model.createProperty(SpdxConstants.SPDX_NAMESPACE + SpdxConstants.PROP_RELATIONSHIP_TYPE));
-	            	if (relatedElement.getURI().equals(file.getURI()) &&
+	            	if (relatedElement.isURIResource() && relatedElement.getURI().equals(file.getURI()) &&
 	            			relationshipType.getURI().equals(RelationshipType.CONTAINS.getIndividualURI())) {
 	            		foundContainsRelationships.add(stmt);
             		}