   {% for invitation in invitations %}
            <tr>
              {% if invitation.user %}
                <td>
                  <a href="{{ invitation.user.get_absolute_url }}">{{ invitation.user.username }}</a>
                </td>
                <td>{{ invitation.user.full_name }}</td>
                <td>{{ invitation.user.email }}</td>
              {% else %}
                <td></td>
                <td></td>
                <td>{{ invitation.email }}</td>
              {% endif %}
           