Updated mediawiki/extensions
Project: mediawiki/extensions/CentralNotice  2e2e50b9be178ef7def263b9f50d834a6c987e36
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Class only loaded when using Translate

BannerMessageGroup is only loaded when CentralNotice is using the
translate extension. Therefore we must gate statements that rely
on it. Apparently I missed one. :p

Change-Id: If650a49354fb1348e257020671d7a65abbc47c74