Error-displayin warning on a specific page

I have a recent blog (2 weeks ago), at:
https://doctorcueva.com

And there is this message displaying above the header:

“Warning: mysqli_num_fields() expects parameter 1 to be mysqli_result, boolean given in /home/luiscuev/public_html/doctorcueva/wp-includes/wp-db.php on line 3078”

But it shows just in the blog posts page at:
https://doctorcueva.com/blog.

It doesn´t display in the homepage, nor about page nor individual posts.
I am using the following plugins:
w3 total cache, Thrive content builder, Genesis supercustomizer, Genesis simple sidebars, plugin organizer, pirate forms. And Genesis child theme. All plugins, themes and wordpress version are updated.

Any idea what´s the problem? I´m not a programmer, but have some notions of html and use wordpress long time ago.

Thanks.