Bootstrap 4 does not use hidden any more
Bootstrap 3 used a class="hidden" attribute to hide content:
Bootstrap 4 uses class="d-none":
</thead>
<tbody>
- <tr class="hidden empty-form">
+ <tr class="d-none empty-form">
{% for field in formset.empty_form %}
{% include 'bootstrap4/field.html' with tag="td" form_show_labels=False %}
{% endfor %}
