Add extra checks for NPE on getUri()

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

Author: goneall

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

@@ -232,7 +232,7 @@ public List<String> getClassUriRestrictions(String classUri, String propertyUri)
 		addPropertyRestrictions(ontClass, property, propertyRestrictions);
 		List<String> retval = new ArrayList<String>();
 		for (Statement stmt:propertyRestrictions) {
-			if (stmt.getPredicate().equals(ON_CLASS_PROPERTY)) {
+			if (stmt.getPredicate().equals(ON_CLASS_PROPERTY) && stmt.getObject().asResource().isURIResource()) {
 				retval.add(stmt.getObject().asResource().getURI());
 			}
 		}
@@ -266,7 +266,7 @@ public List<String> getDataUriRestrictions(String classUri, String propertyUri)
 		addPropertyRestrictions(ontClass, property, propertyRestrictions);
 		List<String> retval = new ArrayList<String>();
 		for (Statement stmt:propertyRestrictions) {
-			if (stmt.getPredicate().equals(ON_DATA_RANGE_PROPERTY)) {
+			if (stmt.getPredicate().equals(ON_DATA_RANGE_PROPERTY) && stmt.getObject().asResource().isURIResource()) {
 				retval.add(stmt.getObject().asResource().getURI());
 			}
 		}