How to set optional data page to route file?

I created my routes.yaml as below,

routes:
  /about/:
    template: about
    data: page.about-page

It works fine when exists a page in the database which has slug is ‘about-page’. But i want to know, how to set data page optionally?

Hey, there! Can you say more about what you’re trying to do?

I’m trying to set static routing with getting meta details from a page. I want to get meta data from the page if exist on the database. else executing with default meta data.