Set registrationInstanceId on Add Registrant Page

{% comment %}Necessary for setting the registrationInstanceId on the internal Add Registrant Page{% endcomment %}
{% if registrationInstanceId == '' %}
{% assign registrationId = 'Global' | PageParameter:'RegistrationId' %}
    {% registration Id:'{{ registrationId }}' securityenabled:'false %}
    {% assign registrationInstanceId = registration.RegistrationInstanceId %}
    {% endregistration %}
{% endif %}