I saw my server log show:
Warning: count(): Parameter must be an array or an object that implements Countable in extensions/Flow/includes/TemplateHelper.php:322 PHP 1. {main}() index.php:0 PHP 2. MediaWiki->run() index.php:42 PHP 3. MediaWiki->main() includes/MediaWiki.php:524 PHP 4. MediaWiki->performRequest() includes/MediaWiki.php:861 PHP 5. MediaWiki->performRequest() includes/MediaWiki.php:294 PHP 6. Flow\Actions\FlowAction->show() includes/MediaWiki.php:500 PHP 7. Flow\Actions\FlowAction->showForAction() extensions/Flow/includes/Actions/Action.php:50 PHP 8. Flow\View->show() extensions/Flow/includes/Actions/Action.php:112 PHP 9. Flow\View->renderApiResponse() extensions/Flow/includes/View.php:81 PHP 10. Flow\TemplateHelper->Flow\{closure}() extensions/Flow/includes/View.php:355 PHP 11. Flow\TemplateHelper->{closure:extensions/Flow/handlebars/compiled/flow_block_loop.handlebars.php:1-29}() extensions/Flow/includes/TemplateHelper.php:113 PHP 12. LCRun3::sec() extensions/Flow/handlebars/compiled/flow_block_loop.handlebars.php:26 PHP 13. Flow\TemplateHelper->{closure:extensions/Flow/handlebars/compiled/flow_block_loop.handlebars.php:25-26}() vendor/zordius/lightncandy/src/lightncandy.php:2485 PHP 14. LCRun3::ch() extensions/Flow/handlebars/compiled/flow_block_loop.handlebars.php:25 PHP 15. Flow\TemplateHelper::block() vendor/zordius/lightncandy/src/lightncandy.php:2602 PHP 16. Flow\TemplateHelper::processTemplate() extensions/Flow/includes/TemplateHelper.php:302 PHP 17. call_user_func:{extensions/Flow/includes/TemplateHelper.php:187}() extensions/Flow/includes/TemplateHelper.php:187 PHP 18. Flow\TemplateHelper->Flow\{closure}() extensions/Flow/includes/TemplateHelper.php:187 PHP 19. Flow\TemplateHelper->{closure:extensions/Flow/handlebars/compiled/flow_block_topic_moderate_post.handlebars.php:1-243}() extensions/Flow/includes/TemplateHelper.php:113 PHP 20. LCRun3::hbch() extensions/Flow/handlebars/compiled/flow_block_topic_moderate_post.handlebars.php:241 PHP 21. Flow\TemplateHelper::eachPost() vendor/zordius/lightncandy/src/lightncandy.php:2718 PHP 22. count() extensions/Flow/includes/TemplateHelper.php:322
I using MW 1.31 and PHP 7.2.10. I think this issue also includes in master. P.S. PHPUnit test can't find it.