Updated mediawiki/extensions
Project: mediawiki/extensions/Flow  0f5137519971f0593f19861364875f96b9561491

Fix problem when submitting a topic without first post.

Exception Caught: Expected PostRevision but received Flow\NotificationController

If a topic is submitted without first post, $firstPost will be null. That's
acceptable.

Bug: 62794
Change-Id: I0a0618036299e36c685389ec2bb70a871a3f761a