MediaWiki internal error.

Original exception: [2000ff3a] /index.php?title=Spezial:Beobachtungsliste Exception from line 346 of /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/specialpage/SpecialPage.php: Please <a href="/index.php?title=Spezial:Anmelden&amp;returnto=Spezial%3ABeobachtungsliste" title="Spezial:Anmelden">anmelden</a> to view or edit items on your watchlist.
Backtrace:
#0 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/specials/SpecialWatchlist.php(44): SpecialPage->requireLogin(Message)
#1 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/specialpage/SpecialPage.php(379): SpecialWatchlist->execute(NULL)
#2 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/specialpage/SpecialPageFactory.php(503): SpecialPage->run(NULL)
#3 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/Wiki.php(285): SpecialPageFactory::executePath(Title, RequestContext)
#4 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/Wiki.php(588): MediaWiki->performRequest()
#5 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/Wiki.php(447): MediaWiki->main()
#6 /www/htdocs/w0159ac1/wiki-goettingen.de/update/index.php(46): MediaWiki->run()
#7 {main}

Exception caught inside exception handler: [bf309271] /index.php?title=Spezial:Beobachtungsliste Exception from line 222 of /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/Hooks.php: Detected bug in an extension! Hook wfSetupImageMap has invalid call signature; Parameter 1 to wfSetupImageMap() expected to be a reference, value given
Backtrace:
#0 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/GlobalFunctions.php(4013): Hooks::run(string, array, NULL)
#1 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/parser/Parser.php(275): wfRunHooks(string, array)
#2 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/StubObject.php(99): Parser->firstCallInit()
#3 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/StubObject.php(119): StubObject->_call(string, array)
#4 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/cache/MessageCache.php(1023): StubObject->__call(string, array)
#5 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/cache/MessageCache.php(1000): MessageCache->getParser()
#6 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/Message.php(977): MessageCache->transform(string, boolean, Language, Title)
#7 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/Message.php(669): Message->transformText(string)
#8 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/Message.php(732): Message->toString()
#9 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/OutputPage.php(855): Message->text()
#10 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/OutputPage.php(900): OutputPage->setHTMLTitle(Message)
#11 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/OutputPage.php(2166): OutputPage->setPageTitle(string)
#12 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/OutputPage.php(2195): OutputPage->prepareErrorPage(Message)
#13 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/exception/ErrorPageError.php(58): OutputPage->showErrorPage(Message, Message, array)
#14 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/exception/MWExceptionHandler.php(44): ErrorPageError->report()
#15 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/exception/MWExceptionHandler.php(139): MWExceptionHandler::report(UserNotLoggedIn)
#16 /www/htdocs/w0159ac1/wiki-goettingen.de/update/includes/Wiki.php(454): MWExceptionHandler::handle(UserNotLoggedIn)
#17 /www/htdocs/w0159ac1/wiki-goettingen.de/update/index.php(46): MediaWiki->run()
#18 {main}