upgrade

In some cases, when e.g. objects are quicky deleted after updates, the

object might be already be deleted when being tried to trigger a

DELETE operation in the search queue. as a consequence, one can sometimes

observer errors like the one below. The new code double-checks now,

if the object for the DELETE operation still exists.

ERROR: insert or update on table "search_observer_queue" violates foreign key constraint "search_observer_queue_object_id_fk"

: DETAIL: Key (object_id)=(497509146) is not present in table "acs_objects".

: CONTEXT: SQL statement "insert into search_observer_queue (