So far twice reported in OTRS. I haven't been able to reproduce this myself (switched device language to German) but it seems that there is an issue with the languages_list.xml table lookup.
The interesting part of the stack trace is:
~~~~
java.lang.RuntimeException: WikiCode de + not found+
at org.wikipedia.WikipediaApp.findWikiIndex(WikipediaApp.java:275)
at org.wikipedia.settings.LanguagePreference.<init>(LanguagePreference.java:26)
git SHA: 5df0d7b3
I think we should consider default to English instead of throwing a RuntimeException in this case.
From OTRS:
2014053010015204: https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketZoom&TicketID=7580023
2014060410002588: https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketZoom;TicketID=7587157
Version: Alpha
Severity: normal