ol: Fix type error in org-link-search corner case
* lisp/ol.el (org-link-search): Account for orphan #+name keyword.
If #+name is followed by a blank line (making it an invalid affiliated
keyword), :name is nil.
Reported-by: Dima Kogan <dima@secretsauce.net>
Ref: https://orgmode.org/list/875z5xf7f7.fsf@secretsauce.net