Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  25e52a1409249157ee0550bd7fb9ab24c312531f

do null check for invalid site, instead of false

if an invalid site, then null is returned and check for it here.

Change-Id: I1b32a7f5ee7c6b2fb3128104ce1fb85f361bad81