( ! ) Warning: [mysql error 1054] Unknown column 'cf.user_id' in 'on clause'

SELECT
    cf.name AS cf_name,
    cf.email AS cf_email,
    u.username AS u_name,
    u.mail_address AS u_email
  FROM piwigo_contact_form AS cf
  LEFT JOIN piwigo_users AS u
    ON cf.user_id = u.id
 in /home/bruno/www/include/dblayer/functions_mysqli.inc.php on line 864
Call Stack
#
Time
Memory
Function
Location
1
0.0001
359256
{main}(  )
.../index.php:0
2
0.0001
360064
include_once( '/home/bruno/www/include/common.inc.php' )
.../index.php:11
3
0.0168
994416
trigger_notify(  )
.../common.inc.php:293
4
0.0170
1012360
contact_form_init(  )
.../functions_plugins.inc.php:264
5
0.0172
1012736
get_contact_emails(  )
.../main.inc.php:78
6
0.0172
1012992
query2array(  )
.../functions.inc.php:308
7
0.0172
1012992
pwg_query(  )
.../functions_mysqli.inc.php:905
8
0.0175
1013040
my_error(  )
.../functions_mysqli.inc.php:149
9
0.0175
1013360
trigger_error
(  )
.../functions_mysqli.inc.php:864