WP_User_Query to exclude users with no posts

I see that it is possible to sort a user query by the number of posts each user has, but is it possible to exclude users with zero posts from the result? In the Wp_User_Query class there is a pre_user_query action, but query strings are a huge weak point, so I’m not sure what sort of filter action I’d want to use here.

If Modified Since HTTP Header

I am trying to enable 304 If Modified Since HTTP header in my WordPress site. After doing lot of Googling I find out a site where the author said to put the following line at the very end of wordpress wp-config.php file. Here is the line of code: