Updated mediawiki/extensions
Project: mediawiki/extensions/Wikibase  4378df8f3f3b572cf29a77d76e354c8cb4a69055

Avoid showing "null" in JavaScript tooltip for properties with no label.
Introduce new utility function that returns plain text and use it where
apropriate.

Change-Id: Ia525f00b73f05d815ffaaa57809dd1712adb02bc