Updated mediawiki/extensions
Project: mediawiki/extensions/Flow  c2e5215f69fd2484bb3d74cd75cb4ab37a1e5bd0

Prepare to drop workflow_user_* fields

A followup patch[1] will drop these fields completely.  This patch
makes them nullable so that the followup patch can stop inserting to
them. Once the followup is applied these fields will be removed 
completely. A bug[2] has also been filed to have this change applied
in WMF production.



[1] I7c759b46995c045405426239e95f40147e8aaecb
[2] https://bugzilla.wikimedia.org/show_bug.cgi?id=72842

Change-Id: Ib5d2d101def3c331a3128b80101ee7b2d093aee9