Add ability to patch an entry with more fields

Like when we create an entry, we can now patch an entry with new fields:
- content
- language
- preview_picture
- published_at
- authors

src/Wallabag/CoreBundle/Helper/ContentProxy.php

@@ -105,7 +105,7 @@ class ContentProxy
             }
         }
 
-        if (!empty($content['authors'])) {
+        if (!empty($content['authors']) && is_array($content['authors'])) {
             $entry->setPublishedBy($content['authors']);
         }