Log from Translatewiki.net,
","exception_id":"1189ee8b06d3ca69fc3fcf12","exception_url":"/w/i.php?title=Special:Translations&message=MediaWiki%3AUpload","caught_by":"mwe_handler"} [] [18-Aug-2019 12:19:45 UTC] PHP Warning: array_keys() expects parameter 1 to be array, null given in /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php on line 493 [2019-08-18 12:19:45] error.ERROR: [1189ee8b06d3ca69fc3fcf12] /w/i.php?title=Special:Translations&message=MediaWiki%3AUpload ErrorException from line 494 of /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php: PHP Warning: Invalid argument supplied for foreach() {"exception":"[object] (ErrorException(code: 0): PHP Warning: Invalid argument supplied for foreach() at /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php:494) [stacktrace] #0 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php(494): MWExceptionHandler::handleError(2, 'Invalid argumen...', '/srv/mediawiki/...', 494, Array) #1 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php(439): MessageCache->loadFromDB('yua', NULL) #2 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php(359): MessageCache->loadFromDBWithLock('yua', Array, NULL) #3 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php(1049): MessageCache->load('yua') #4 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php(976): MessageCache->getMsgFromNamespace('Translate-docum...', 'yua') #5 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php(946): MessageCache->getMessageForLang(Object(Language), 'translate-docum...', true, Array) #6 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/cache/MessageCache.php(888): MessageCache->getMessageFromFallbackChain(Object(Language), 'translate-docum...', true) #7 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/language/Message.php(1310): MessageCache->get('translate-docum...', true, Object(Language)) #8 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/language/Message.php(865): Message->fetchMessage() #9 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/language/Message.php(969): Message->toString('plain') #10 /srv/mediawiki/tags/2019-08-15_08:46:28/extensions/Translate/TranslateHooks.php(527): Message->plain() #11 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/Hooks.php(174): TranslateHooks::translateMessageDocumentationLanguage(Array, 'yua') #12 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/Hooks.php(202): Hooks::callHook('LanguageGetTran...', Array, Array, NULL) #13 /srv/mediawiki/tags/2019-08-15_08:46:28/languages/Language.php(880): Hooks::run('LanguageGetTran...', Array) #14 /srv/mediawiki/tags/2019-08-15_08:46:28/languages/Language.php(849): Language::fetchLanguageNamesUncached('yua', 'all') #15 /srv/mediawiki/tags/2019-08-15_08:46:28/languages/Language.php(943): Language::fetchLanguageNames('yua', 'all') #16 /srv/mediawiki/tags/2019-08-15_08:46:28/languages/Language.php(435): Language::fetchLanguageName('yua', 'yua') #17 /srv/mediawiki/tags/2019-08-15_08:46:28/extensions/Translate/specials/SpecialTranslations.php(245): Language::isKnownLanguageTag('yua') #18 /srv/mediawiki/tags/2019-08-15_08:46:28/extensions/Translate/specials/SpecialTranslations.php(78): SpecialTranslations->showTranslations(Object(Title)) #19 /srv/mediawiki/tags/2019-08-15_08:46:28/includes/specialpage/SpecialPage.php(571): SpecialTranslations->execute('')
Need to investigate and see if this is caused due to an upstream issue / change