Fall back to language code in wikibase.getLanguageNameByCode()

wikibase.getLanguageNameByCode() is used to fill messages. If ULS is not loaded,
those messages would contain en empty string.

Change-Id: I156e29d1a1a02e20461146c581608f66cff6d337
Merge "Fall back to language code in wikibase.getLanguageNameByCode()"