If you already have "closed" column in gm_tickets table, use ALTER TABLE `gm_tickets` CHANGE `closed` `closed` tinyint(1) NOT NULL default '0';
If you do not have that column, use ALTER TABLE `gm_tickets` ADD `closed` tinyint(1) NOT NULL default '0' AFTER `timestamp`;
Also, you should check if you have "assignedto" column.
--HG--
branch : trunk