After you upgrade to Ektron 9.10, an error may occur when you choose Workarea > Settings > Community Management and click on Community Groups (see screenshot). The error is caused by retrieving a group at Ektron.Cms.Community.CommunityGroupAPI.GetAllCommunityGroups.
Make backup of the current database and then apply the following SQL statements.
update community_group_tbl set enable_calendar = 0 where enable_calendar is NULL
update community_group_tbl set enable_todolist = 0 where enable_todolist is NULL