Fix #356

src/main/java/de/dhbwstuttgart/syntaxtree/factory/ASTFactory.java

@@ -176,8 +176,9 @@ public class ASTFactory {
 		for (Type jreInterface : jreClass.getGenericInterfaces()) {
 			implementedInterfaces.add((RefType) createType(jreInterface));
 		}
-		List<RefType> permittedSubtypes = new ArrayList<>();
+		List<RefType> permittedSubtypes = null;
 		if (jreClass.isSealed()) {
+			permittedSubtypes = new ArrayList<>();
 			for (Class subclass : jreClass.getPermittedSubclasses()) {
 				permittedSubtypes.add((RefType) createType(subclass));
 			}