Display First posts without the default featured image

note: Your code is not a loop, it’s a query to get a list of posts.

In your template there should be a loop (using that list of posts) with a function to call the featured image. This is where you should change the template, and remove the call to the featured image.

If you are only trying to select posts with no featured image, it is a completely different case. I’m not sure it can be done with a query. A simpler solutions could be to write a if-statement in your loop, to check if post has a featured image, if not, showing the post. This isn’t a pretty solution, because it could be possible that you query 20 posts, but since all have a featured image, none will be displayed.