Avoid NPE when getting localized name

[twz123]

The package reference is not guaranteed to be present.

Exception in thread "main" java.lang.NullPointerException
	at lsifjava.DocumentIndexer.getLocalizedName(DocumentIndexer.java:514)
	at lsifjava.DocumentIndexer.appendTypeParam(DocumentIndexer.java:505)
	at lsifjava.DocumentIndexer.mkClassDoc(DocumentIndexer.java:472)
	at lsifjava.DocumentIndexer.access$4(DocumentIndexer.java:446)
	at lsifjava.DocumentIndexer$DefinitionsVisitor.visitCtClass(DocumentIndexer.java:205)
	at spoon.support.reflect.declaration.CtClassImpl.accept(CtClassImpl.java:58)
	at spoon.reflect.visitor.CtScanner.scan(CtScanner.java:177)
	at spoon.reflect.visitor.CtScanner.scan(CtScanner.java:169)
	at spoon.reflect.visitor.CtScanner.scan(CtScanner.java:142)
	at spoon.reflect.visitor.CtScanner.visitCtClass(CtScanner.java:335)
	at lsifjava.DocumentIndexer$DefinitionsVisitor.visitCtClass(DocumentIndexer.java:196)
	at spoon.support.reflect.declaration.CtClassImpl.accept(CtClassImpl.java:58)
	at lsifjava.DocumentIndexer.visitDefinitions(DocumentIndexer.java:55)
	at lsifjava.ProjectIndexer.index(ProjectIndexer.java:125)
	at lsifjava.Main.main(Main.java:19)

[Strum355]

Thanks for the fix! Much appreciated : ) 🎉