When adding element "Clock" to the screen there is possibility to specify empty host name in the "Parameter" field when creating "Clock" resource of the "Time type=Host time" - it is possible to leave this field empty and save screen configuration, screen will be saved, but below this screen will appear error messages:

• reset() expects parameter 1 to be array, null given[C:\Program Files\Xampp\xampp\htdocs\Zabbix\ZBX-3500\frontends\php\include\screens.inc.php:1474]
• Undefined index: lastvalue[C:\Program Files\Xampp\xampp\htdocs\Zabbix\ZBX-3500\frontends\php\include\screens.inc.php:1482]
• Undefined index: lastvalue[C:\Program Files\Xampp\xampp\htdocs\Zabbix\ZBX-3500\frontends\php\include\screens.inc.php:1488]