(I have a fix ready, I'm making a task for record purposes.)

When MediaWiki is running on PHP 7.2 or above, and MediaWiki:Refreshed-wiki-dropdown is empty, Refreshed will render incorrectly. Specifically you get the warning "Warning: count(): Parameter must be an array or an object that implements Countable [...]." This breaks the page.

This is because per the count() docs, as of PHP 7.2, count() yields a warning when an element is passed in that's not an array or Countable. (This issue hasn't popped up on sites like Brickimedia since they use older versions of PHP.) The culprit is this line in RefreshedTemplate.php:

wfDebugLog( 'Refreshed', sprintf( 'Get %s, which contains %s lines', $messageKey, count( $lines ) ) );

$lines is sometimes null, which is not an array or Countable. Specifically it's null when MediaWiki:Refreshed-wiki-dropdown is empty. Then $count( $lines ) yields a warning, breaking the page.

To fix this issue, a check should be added to RefreshedTemplate.php to see if $lines is null before the above line is run.