Fix PHP Warning: Parameter must be an array or an object that implements Countable

[joshfeck]

Fixes #659. This branch was tested on a server with PHP 7.2. View a single post with a featured image, with WP_DEBUG set to true.

[glueckpress]

If the intention is to count the number of responses, why change it to counting the number of authors instead? Just dumping count() did the trick for me locally. Since $discussion->responses returns a string value (which probably should be reviewed), wrapping it in absint() ensures we get an integer:

<div class="<?php echo ( ! empty( $discussion ) && absint( $discussion->responses ) > 0 ) ? 'entry-header has-discussion' : 'entry-header'; ?>">

[joshfeck]

I made your suggested change. Since you asked, the author count seemed more reliable at the time because $discussion->responses is derived from get_comment_count() and its return value can be filtered.

What can happen is another plugin, like muut, will filter the count to be zero (or even a placeholder to be filled later with JS). So there's a chance a post with comments will have a filtered value be zero, but that's probably an edge case. Worse case scenario is the CSS class won't be added there.