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 ('1683b84a7eb60471b350e8037fa0ee31', -1, 1537833661, 1537833661, '3650537b', 78, 0, 0)

Line : 187
File : sessions.php