Firefox 29, Win 7:
On https://de.wikipedia.org/wiki/Ata_Demirer?debug=true#mediaviewer/Datei:Ata_Demirer_01.jpg on opening mediaviewer.
Firebug shows:
TypeError: mw.config.get(...)[this.namespace] is undefined
https://bits.wikimedia.org/static-1.24wmf6/resources/src/mediawiki.api/mediawiki.api.js
Line 222
(at "apiDeferred.resolve( result, jqXHR );")
caused problem: not yet known.
Version: master
Severity: normal