php notice fixings

addons:
- bufferapp (missing errorcode)
- twitter (wrong field name 'nickname')
core:
- bbcode (incomplete attachementdata)
- crypto (uninitialized key)

buffer/bufferapp.php

@@ -42,6 +42,7 @@
 		public $errors = [
 			'invalid-endpoint' => 'The endpoint you supplied does not appear to be valid.',
 
+			'401' => 'Unauthorized.',
 			'403' => 'Permission denied.',
 			'404' => 'Endpoint not found.',
 			'405' => 'Method not allowed.',

twitter/twitter.php

@@ -1900,7 +1900,7 @@ function twitter_update_mentions($body)
 function twitter_convert_share(array $attributes, array $author_contact, $content, $is_quote_share)
 {
 	if ($author_contact['network'] == Protocol::TWITTER) {
-		$mention = '@' . $author_contact['nickname'];
+		$mention = '@' . $author_contact['nick'];
 	} else {
 		$mention = $author_contact['addr'];
 	}