Reproduction procedure

• Use MySQL
• "Time zone data":https://dev.mysql.com/doc/refman/5.6/en/mysql-tzinfo-to-sql.html is not loaded
• Change user language from UTC to something else
• Group by created_on at issues/index

When the above conditions are met, the group_count badge will be displayed as empty as shown in the screenshot.
!{width: 500px; border: 1px solid #ccc}ScreenShot-2019-08-29-10.49.27.png!

It doesn't matter if group_count is nil because MySQL doesn't get group_count if it doesn't load time zone data.
The problem is that an empty badge is displayed at that time.

Badge should also be hidden if group_count is not successfully acquired(like "timelog":http://www.redmine.org/projects/redmine/repository/entry/trunk/app/views/timelog/_list.html.erb#L25).

This is a problem with trunk.