Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  5694c9c44ed12f924cf6dacf11fa3ca4f1c241f9

Unify top factory getter implementations

The fact that the variables can be null should be documented in my
opinion.

The fact that they are null by default should be written down
explicitely, in my opinion.

The check should be done with "=== null", in my opinion, not with
"!" (it's not a bool) and not with "isset".

Change-Id: Ib5bb23de7b32b03706ea8126434b05b35efdf9da