Webmin after update «Error — Perl execution failed»

Error - Perl execution failed
Undefined subroutine &main::authentic called at /usr/share/webmin/authentic-theme/index.cgi line 12

Fix is simple:

Just remove all preroot_ and theme_ from configs (/etc/webmin/miniserv.conf) and make sure that preroot and theme set to authentic-theme. The problem is that why this is happening.