We guess this might be a bug.
http://demo.geeklog.net/admin/plugins/forum/boards.php
-> select Blank group
-> error
Discussion Forum Board Admin
An SQL error has occurred. Please see error.log for details.
Text Formatted Code
layout/xxxx/forum/layout/admin/boards_edtforum.thtml
<OPTION value="{groupname}" SELECTED>{groupname}{grouplist}
->
{grouplist}
Report by tsuchi (Geeklog.jp)
Geeklog Japan
https://www.geeklog.jp