From Perupedia

Detected bug in an extension! Hook efCategoryTreeParserOutput failed to return a value; should return true to continue hook processing or false to abort.

Backtrace:

#0 /home/content/83/2784283/html/perupedia/includes/OutputPage.php(1113): wfRunHooks('OutputPageParse...', Array)

#1 /home/content/83/2784283/html/perupedia/includes/OutputPage.php(1122): OutputPage->addParserOutputNoText(Object(ParserOutput))

#2 /home/content/83/2784283/html/perupedia/includes/Article.php(4008): OutputPage->addParserOutput(Object(ParserOutput))

#3 /home/content/83/2784283/html/perupedia/includes/Article.php(1348): Article->outputWikiText(''''Juan Belmont...', true, Object(ParserOptions))

#4 [internal function]: Article->doViewParse()

#5 /home/content/83/2784283/html/perupedia/includes/PoolCounter.php(59): call_user_func(Array)

#6 /home/content/83/2784283/html/perupedia/includes/Article.php(903): PoolCounter_Stub->executeProtected(Array, Array)

#7 /home/content/83/2784283/html/perupedia/includes/Wiki.php(493): Article->view()

#8 /home/content/83/2784283/html/perupedia/includes/Wiki.php(70): MediaWiki->performAction(Object(OutputPage), Object(Article), Object(Title), Object(User), Object(WebRequest))

#9 /home/content/83/2784283/html/perupedia/index.php(117): MediaWiki->performRequestForTitle(Object(Title), Object(Article), Object(OutputPage), Object(User), Object(WebRequest))

#10 {main}