fix object storage nil pointer deref error
diff --git a/openstack/objectstorage/v1/containers/requests.go b/openstack/objectstorage/v1/containers/requests.go
index bbf8cdb..50ff9f4 100644
--- a/openstack/objectstorage/v1/containers/requests.go
+++ b/openstack/objectstorage/v1/containers/requests.go
@@ -114,7 +114,9 @@
 		MoreHeaders: h,
 		OkCodes:     []int{201, 202, 204},
 	})
-	res.Header = resp.Header
+	if resp != nil {
+		res.Header = resp.Header
+	}
 	res.Err = err
 	return res
 }
@@ -180,7 +182,9 @@
 		MoreHeaders: h,
 		OkCodes:     []int{201, 202, 204},
 	})
-	res.Header = resp.Header
+	if resp != nil {
+		res.Header = resp.Header
+	}
 	res.Err = err
 	return res
 }
@@ -193,7 +197,9 @@
 	resp, err := c.Request("HEAD", getURL(c, containerName), gophercloud.RequestOpts{
 		OkCodes: []int{200, 204},
 	})
-	res.Header = resp.Header
+	if resp != nil {
+		res.Header = resp.Header
+	}
 	res.Err = err
 	return res
 }