The source project of this merge request has been removed.
The spec says that upon StartTLS 'success', both TLS communications is established on the octet following the Start TLS response (and the request)... and that once one starts TLS communications, one can never go back to LDAP without TLS. So if there's a TLS failure (whether as part of TLS nego or later), LDAP communications cannot be continued (without TLS).
Only ignoring LDAP errors (rc > 0) ensures that if TLS negotiation fails, we don't attempt to send LDAP operations without TLS.