Noticed this on one of our gpl servers - this is a very lightweight server and is only used to manage our dns zones. Was in the webmin menu and noticed this section (Webmin Servers Index) is greyed out and not accessible. Nothing's been done to this server on our end except normal os/virtualmin updates.
Operating system Ubuntu Linux 18.04.1
Webmin version 1.900
Usermin version 1.741
Virtualmin version 6.04 Authentic theme version 19.21
Perl version 5.026001
Path to Perl /usr/bin/perl
BIND version 9.11