Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  3a65287aaeb3bf6109c8e7ad557100b04f19c47a

Fix warnings and general clean up in ChangeHandler

* Fix warnings by introducing instanceof checks.
* Add missing docs.
* More descriptive variable names.
* Fix parameter order.

Change-Id: If258b63807930aacd89cd24da57a1a27648800d6