Strong Testimonials is my go-to WordPress plugin for displaying testimonials. I use it on my own site and on many client sites.
Today, after updating WordPress to version 5.4 — and updating Strong Testimonials from 2.40.1 to 2.40.2 — on one of those sites, the WordPress dashboard crashed.
The error message:
PHP Fatal error: Call to a member function get() on null in /[path_to_file]/wp-includes/query.php on line 28
By downgrading back to version 2.40.1 of the plugin, I was able to fix the problem.
The plugin author is aware of the problem and is working on the fix.
I will update this post when the new version of the plugin is working properly.