There are [[ https://logstash.wikimedia.org/app/kibana#/discover?_g=(refreshInterval:(display:Off,pause:!f,value:0),time:(from:now-7d,mode:quick,to:now))&_a=(columns:!(_source),index:'logstash-*',interval:auto,query:(query_string:(analyze_wildcard:!t,query:'message:%22Collection%22%20AND%20level:%22NOTICE%22')),sort:!('@timestamp',desc)) | various complaints ]] about undefined indexes in the collection extension:
* [ ] Notice: Undefined index: subtitle in /srv/mediawiki/php-1.30.0-wmf.16/extensions/Collection/templates/CollectionPageTemplate.php on line 30
* [ ] Notice: Undefined index: title in /srv/mediawiki/php-1.30.0-wmf.16/extensions/Collection/templates/CollectionPageTemplate.php on line 29
* [ ] Notice: Undefined index: `$_SESSION['wsCollection']` in /srv/mediawiki/php-1.30.0-wmf.16/extensions/Collection/Collection.php on line 354 (issue inside wfAjaxCollectionGetItemList)
==Developer notes
CollectionSession::getCollection can return [] which will cause the first two notices.
```
$template->set( 'collection', CollectionSession::getCollection() );
```