hentry warning node is empty

I am getting this message from Google Webmaster tools on all posts: hentry: Node is empty. Double check that this is desired and consider removing.

This just started showing up and I am not sure what it is telling me. In the testing tool I get this: <article id=”post-721″ class=”post-721 post type-post status-publish format-standard has-post-thumbnail hentry category-social-media tag-pinterest”>

Has anyone else seen this? Any idea of how to fix it?