Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  6ba28f0ddb6a5f5208841a1af3c74d01889deaaf

Refactor some of MergeItems

This should fix the random failing test on travis
As far as I can tell this was caused by the item used
when testing exceptions not actually existing and
therefor triggering a different error than expected

i.e. item doesnt exist instead of something else

Also tidied some other things up

Change-Id: I9c39ea216f707e339ae9754278a78adbe8cfaf9b