Only show image name as a link when the image exists

Updated the nova api to return None when the image name
is not available, for example, when it's deleted.

Added a check for the image name before showing it as
a link.

Change-Id: I342b23dfd8352182f50c41054d2dbb3eae854839
Closes-bug:1668783

openstack_dashboard/api/nova.py

@@ -118,7 +118,7 @@ class Server(base.APIResourceWrapper):
         from openstack_dashboard.api import glance
 
         if not self.image:
-            return _("-")
+            return None
         if hasattr(self.image, 'name'):
             return self.image.name
         if 'name' in self.image:
@@ -129,7 +129,7 @@ class Server(base.APIResourceWrapper):
                 return image.name
             except (glance_exceptions.ClientException,
                     horizon_exceptions.ServiceCatalogException):
-                return _("-")
+                return None
 
     @property
     def internal_name(self):

openstack_dashboard/dashboards/project/instances/templates/instances/_detail_overview.html

@@ -101,7 +101,13 @@
       {% endwith %}
       {% if instance.image %}
         <dt>{% trans "Image Name" %}</dt>
-        <dd><a href="{{ instance.image_url }}">{{ instance.image_name }}</a></dd>
+        <dd>
+        {% if instance.image_name %}
+          <a href="{{ instance.image_url }}">{{ instance.image_name }}</a>
+        {% else %}
+          {% trans "-" %}
+        {% endif %}
+        </dd>
         <dt>{% trans "Image ID" %}</dt>
         <dd>{{ instance.image.id }}</dd>
       {% else %}

openstack_dashboard/test/api_tests/nova_tests.py

@@ -59,7 +59,7 @@ class ServerWrapperTests(test.TestCase):
         self.mox.ReplayAll()
 
         server = api.nova.Server(server, self.request)
-        self.assertEqual('-', server.image_name)
+        self.assertEqual(None, server.image_name)
 
 
 class ComputeApiTests(test.APITestCase):