In the autoregistration branch of add_discovered_host() (in zabbix_server/operations/operations.c), the update hosts statement is built from optional parts separated by delim.

If monitored_by is the first changed field and the TLS settings also change, the next part is appended with a space instead of a comma.

Trigger conditions (all required):
  - hosts.monitored_by differs from the new value.
  - hosts.proxyid and hosts.proxy_groupid both match the new values, so delim is still ' '.
  - hosts.tls_accept differs from the TLS mode of the autoregistration connection.

For a consistent hosts row, the second condition can't occur together with the first, because every change between server, proxy and proxy group also changes proxyid or proxy_groupid. The bug therefore needs a row where monitored_by doesn't match those fields, for example monitored_by=1 with proxyid NULL.

Impact:
  - Failed update: the statement fails with an SQL syntax error, and add_discovered_host() ignores the result zbx_db_execute().
  - Settings not applied: neither the monitored_by nor the TLS/PSK changes are saved, and this can repeat on every autoregistration while the row stays inconsistent.
  - Audit entries: they are still generated for these changes, even though the update failed.

Steps to reproduce:
  1. Create an autoregistered host monitored by the server, with tls_accept=1 (no encryption).
  2. Make the row inconsistent: update hosts set monitored_by=1 where hostid=<hostid>; (proxyid stays NULL).
  3. Configure autoregistration with PSK and an action with the "Add host" operation.
  4. Autoregister the same host directly with the server using PSK.

Actual result: the server log shows an SQL syntax error, and the host is not updated.

Expected result: the host is updated with monitored_by=0 and the new TLS/PSK settings.