How to check if category/tag exists in Jekyll?

I'm trying to achieve a post header like in the example below:

8/18/2018 | Tags: foo, bar

In order to do that I need to make sure tag exists, otherwise | Tags: section waste space in untagged post.

After searching the web, I tried this statement:

But every statement always returns true whether tag declared in front matter.

What should I do to hide the label?