Error-Optional.Get()

I am getting an error as follow:
An error occurred whilst creating the view
IllegalStateException:
Optional.get cannot be called on an absent value

While using a custom RDF/XML File : https://drive.google.com/file/d/163MGS9Myatd-wDwpj5njh8eGp8SHPoWQ/view?usp=sharing
I am using Protege-5.6.1