That seems to be a bug that shows up occasionally, though it’s not reliably reproducible, so it hasn’t been corrected.
The fix is simple though, you can delete the domain ID in “/etc/webmin/virtual-server/domains/”, restart Virtualmin, and then it should be gone from your drop-down list.
Setting up log file rotation ..
.. Log file rotation failed! : .. the log file /var/log/virtualmin/xxxxxxxxxxxx_access_log is already being rotated at /usr/libexec/webmin/web-lib-funcs.pl line 1433.
Delete the log files in /var/log/virtualmin
Delete the user in “User and Group” in webmin
Next step : re-create the virtual server!