phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '0' for key 'session_user_id'

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('a76ea7f3d701cb607eb7b35bdc650ad4', -1, 1534788668, 1534788668, '3651c423', 39, 0, 0)

Line : 187
File : sessions.php