membershipworks: Suppress subtotals in event invoice when there is only one ticket type

membershipworks/templates/membershipworks/tables/invoice_table.dj.html

@@ -2,6 +2,7 @@
 
 {% block table.tfoot %}
   {% if table.has_footer %}
+    {% if table.rows|length > 1 %}
       <tfoot {{ table.attrs.tfoot.as_html }}>
         <tr>
           {% for column in table.columns %}
@@ -16,6 +17,7 @@
             {% endif %}
           {% endfor %}
         </tr>
+      {% endif %}
       {% if table.event.instructor_flat_rate != 0 %}
         <tr class="text-end">
           <td colspan="{{ table.columns|length|add:-2 }}"></td>