of course I can change the error_reporting. But I think the notices should be fixed, even when this is not high priority.
The PHP specification is in constant change, so something is fine with the current version produces a notice with the next release PHP release and the fix for it might cause the software to fail then under older PHP versions. So the only supported and tested error reporting level from ISPConfig is:
error_reporting = E_ALL & ~E_NOTICE