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:322I 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.