• I've read and understood the contribution guidelines.
• I've searched for any related issues and avoided creating a duplicate issue.

Please give us a description of what happened.

In posts page (index.php) when I doesn't have any posts I see error:
Warning: count(): Parameter must be an array or an object that implements Countable in D:\xampp\htdocs\wp-includes\post-template.php on line 284

When I disable Yoast SEO plugin, then this message wont come.
And when I made a post, then this error also goes away.

Technical info

• WordPress version: 4.9.6 (multisite)
• Yoast SEO version: 7.7.2
• PHP version: 7.2.4
• Relevant plugins in case of a bug: Just Yoast SEO. Nothing else.

• Tested with theme: my custom theme, Underscores (https://underscores.me/), UnderStrap (https://understrap.com/) and many others - that's a common issue, not related with themes or plugins.