In empty document completion context will have RazorDocumentSyntax as Owner. RazorDoucmentSyntax has null as the parent, which makes sense. However compiler thinks we can't have a null here, while obviously we do.

I'm adding a null check and a test for this case. We would probably further discuss the implications here. I tried to track down how we get null in a non-nullable field, but it's a bit confusing since the class gets generated.