Steps to reproduce the issue

I've done three Updates:
1.) Akeeba Backup Core package 8.0.6 > 8.0.8
2.) German 4.0.0-rc4.1 > 4.0.0-rc5.1
3.) J!-Core 4.0.0-rc4 > 4.0.0-rc5

4.) Backend: Click on Components > Akeeba Backup > Manage Backups

Expected result

Possibility to see and manage the backups.

Actual result

Can't see the backups, got an error message instead:

"Akeeba Backup - An unhandled Exception has been detected
500 implode(): Argument #1 ($pieces) must be of type array, string given
File <root>/layouts/joomla/form/field/calendar.php Line 107

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Joomla 4.0.0-rc5 – PHP 8.0.8 on Linux

Debug information
Exception type: TypeError

..."

System information (as much as possible)

• Joomla! 4.0.0-rc5 Release Candidate [ Mañana ] 27-July-2021 22:41 GMT
• PHP-Version 8.0.8
• Webserver Apache
• Datenbanktyp mysql

Additional comments

I've got the same problem in another installation of 4.0.0-rc5.