column "waiting" does not exist

I have no idea what is causing this message in the logs (PostgreSQL
9.6+177.pgdg80+1 on Debian):

2017-03-02 10:20:25 SAST [5196-1] [unknown] postgres postgres(at)template1
ERROR: column "waiting" does not exist at character 217
2017-03-02 10:20:25 SAST [5196-2] [unknown] postgres postgres(at)template1
STATEMENT: SELECT tmp.mstate AS state,COALESCE(count,0) FROM
(VALUES
('active'),('waiting'),('idle'),('idletransaction'),('unknown')) AS
tmp(mstate)
LEFT JOIN
(SELECT CASE WHEN waiting THEN 'waiting' WHEN
state='idle' THEN 'idle' WHEN state LIKE 'idle in transaction%' THEN 'idle$
count(*) AS count
FROM pg_stat_activity WHERE pid !=
pg_backend_pid() AND datname='data_portal'
GROUP BY CASE WHEN waiting THEN 'waiting' WHEN
state='idle' THEN 'idle' WHEN state LIKE 'idle in transaction%' THEN 'idl$
) AS tmp2
ON tmp.mstate=tmp2.mstate
ORDER BY 1;

I do not know whether it is related but we recently get warnings about
bloat in our system tables from the monitoring program.

How do I fix the cause of this error message?

Regards
Johann
--
Because experiencing your loyal love is better than life itself,
my lips will praise you. (Psalm 63:3)