* (bug 41966) Follow-up I551a90b0 (c2172d4): fix fatal error in PoolWorkArticleView...

* (bug 41966) Follow-up I551a90b0 (c2172d4): fix fatal error in PoolWorkArticleView::doWork()

The error is Fatal error:  Call to a member function getParserOutput() on a non-object in includes/WikiPage.php on line 3363.

The problem is that if the fifth parameter passed to PoolWorkArticleView::__construct() is not given or is null, which is now
the case since the change mentioned on the first line of this commit summary, the content is fetched from Page::getContent().
When the Page object is a WikiPage instance there is no problem, but when this is an Article instance, Article::getContent()
actually returns the content as *string* and not as object, like it did before the Wikidata branch merge.

Worked arround this by passing the WikiPage object to PoolWorkArticleView from Article::view().

Also removed non-existing sixth parameter to PoolWorkArticleView::__construct().

Change-Id: I537862f519542de4f034be29bba4b75898382f59