fix 'None' output when ip does not exist

abonapp/templates/abonapp/editAbon.html

@@ -148,7 +148,8 @@
                             <div class="col-sm-8 btn-group btn-group-sm">
                                 {% if device %}
                                     <a href="{% url 'devapp:view' group.pk device.pk %}" target="_blank" class="btn btn-sm btn-default" title="{% trans 'Mac Address' %}: {{ device.mac_addr|default:_('Not assigned') }}">
-                                        <span class="glyphicon glyphicon-hdd"></span> <span class="hidden-md">{{ device.comment|truncatechars:11 }} {{ device.ip_address }}</span>
+                                        <span class="glyphicon glyphicon-hdd"></span>
+                                        <span class="hidden-md">{{ device.comment|truncatechars:11 }} {{ device.ip_address|default:'' }}</span>
                                     </a>
                                     <a href="{% url 'abonapp:clear_dev' group.pk abon.username %}" class="btn btn-sm btn-danger">
 					                    <span class="glyphicon glyphicon-remove-circle"></span> <span class="hidden-xs hidden-lg">{% trans 'Remove clutch' %}</span>