mysql Ошибка [1062] : EXECUTE

URI: index.php?option=com_dogpedigree&Itemid=36&task=dog&did=619
Message: Duplicate entry '1-NULL' for key 2
INSERT INTO elx_session ( `session_id`,`time`,`username`,`gid`,`allowed`,`guest`,`ip` ) VALUES ( 'c23cb0a8c2f94d22b900b2af7be200fa','1550733644',NULL,'29','29','1','3.80.38.5' )

mossession::store failed
DB function failed with error number 1062
Duplicate entry '1-NULL' for key 2