Undefined subroutine &virtual_server::valid_mailbox_name called at /opt/webmin/virtual-server/save_u

Hi,

I got this error when I want to create a user in virtualmin. I think this error is since version 3.51.

Error - Perl execution failed

Undefined subroutine &virtual_server::valid_mailbox_name called at /opt/webmin/virtual-server/save_user.cgi line 120.