E_WARNING on New/Edit Tag screen
Warning: count(): Parameter must be an array or an object that implements Countable in include() (line 71 of blah\...\templates_c\en_US\%%4D\4D9\4D941223%%Edit.tpl.php
I think this is new in master or 5.23 and at first glance it's because $parent_tags is null when the template tries to do {if $parent_tags|@count > 0}
(Linking to 5.22.0 since then the ref won't change but I'm not sure yet if this affects 5.22.) https://github.com/civicrm/civicrm-core/blob/5.22.0/templates/CRM/Tag/Form/Edit.tpl#L60
I might first look into why this changed to see if it's something deeper but the obvious quick fix is to check the variable exists first before applying count. Also this is a good candidate for a test as described at #1536 (closed).