Only populate attachments array element if there are attachments

lib/twitterapi.php

@@ -188,8 +188,11 @@ class TwitterapiAction extends Action
 
         # Enclosures
         $attachments = $notice->attachments();
+
+        if (!empty($attachments)) {
+
             $twitter_status['attachments'] = array();
-        if($attachments){
+
             foreach ($attachments as $attachment) {
                 if ($attachment->isEnclosure()) {
                     $enclosure = array();