@Override
            public void xmlPropertySet( String property, Map<String, Object> params )
            {}
Java's SaslServer does not allow for null values. This makes it hard to distinguish between an empty (initial)
responses (represented in XMPP as a single equals sign character '=', as per RFC-6120 section 6.4.2), and a
missing/absent response. This can be problematic when a SASL mechanism implementation is to act differently on each
scenario (like the EXTERNAL mechanism, that is to challenge for an authzid when no initial response is provided,
but which is to use the stream's 'from' attribute value when the initial response is empty). To work around this
shortcoming in Java's SASL implementation, this class will add a session attribute using a key that has the name
of this constant's value when it detects a Sasl response that is present, but empty.

@see <a href="https://igniterealtime.atlassian.net/jira/software/c/projects/OF/issues/OF-2514">OF-2514: Differentiate between missing and empty initial SASL response</a>
xmppserver/src/main/java/org/jivesoftware/openfire/net/SASLAuthentication.java