Avoid printing notify object in lang selector on error (elastic#8960)

Backports PR elastic#8639

**Commit 1:**
Avoid printing notify object in lang selector on error

When ES is unavailable and we can't get the list of enabled scripting
langs we display a notification to the user. We were also accidentally
returning that notification object from the service method and
displaying its toString representation in the language select drop down.
Now we simplay return an empty array so the dropdown is rendered without
options.

Fixes elastic#8636

* Original sha: 051c554
* Authored by Matthew Bargar <[email protected]> on 2016-10-12T15:25:15Z

src/ui/public/field_editor/field_editor.js

@@ -162,7 +162,8 @@ uiModules
         return $http.get(chrome.addBasePath('/api/kibana/scripts/languages'))
         .then((res) => res.data)
         .catch(() => {
-          return notify.error('Error getting available scripting languages from Elasticsearch');
+          notify.error('Error getting available scripting languages from Elasticsearch');
+          return [];
         });
       }