Warning:  [mysql error 1054] Unknown column 'user_agent' in 'field list'

SELECT
    user_agent,
    COUNT(*) AS counter,
    MIN(occured_on) AS first_encounter,
    MAX(occured_on) AS last_encounter
  FROM piwi_activity
  WHERE user_agent NOT LIKE 'Mozilla/5%'
  GROUP BY user_agent
; in /web/eac57/piwi/include/dblayer/functions_mysqli.inc.php on line 847

Fatal error: Uncaught Error: Call to a member function fetch_assoc() on bool in /web/eac57/piwi/include/dblayer/functions_mysqli.inc.php:913 Stack trace: #0 /web/eac57/piwi/include/functions.inc.php(2873): query2array('\nSELECT\n use...') #1 /web/eac57/piwi/include/page_tail.php(58): send_piwigo_infos() #2 /web/eac57/piwi/index.php(442): include('/web/eac57/piwi...') #3 {main} thrown in /web/eac57/piwi/include/dblayer/functions_mysqli.inc.php on line 913