protected boolean verifySpnegoAttributeValue(final LdapAttribute attribute) {
        return attribute != null && StringUtils.isNotBlank(attribute.getStringValue());
    }
Verify spnego attribute value.
This impl makes sure the attribute exists and has a value.

@param attribute the ldap attribute
@return true if available. false otherwise.
support/cas-server-support-spnego-webflow/src/main/java/org/apereo/cas/web/flow/client/LdapSpnegoKnownClientSystemsFilterAction.java