Ignore containers that don't have a name

If a container is in the process of being removed, or removal has
failed, it can sometimes appear in the output of GET /containers/json
but not have a 'Name' key. In that case, rather than crashing, we can
ignore it.

Signed-off-by: Aanand Prasad <aanand.prasad@gmail.com>

compose/container.py

@@ -22,10 +22,14 @@ class Container(object):
         """
         Construct a container object from the output of GET /containers/json.
         """
+        name = get_container_name(dictionary)
+        if name is None:
+            return None
+
         new_dictionary = {
             'Id': dictionary['Id'],
             'Image': dictionary['Image'],
-            'Name': '/' + get_container_name(dictionary),
+            'Name': '/' + name,
         }
         return cls(client, new_dictionary, **kwargs)