==== Error ====
* mwversion: `1.37.0-wmf.19`
* reqId: `b506d8a6-a35b-4011-b017-2b6160d6ff09`
* [[ https://logstash.wikimedia.org/app/dashboards#/view/AXFV7JE83bOlOASGccsT?_g=(time:(from:'2021-08-24T15:42:57.000Z',to:'2021-08-25T15:51:58.887Z'))&_a=(query:(query_string:(query:'reqId:%22b506d8a6-a35b-4011-b017-2b6160d6ff09%22'))) | Find reqId in Logstash ]]
* [[ https://logstash.wikimedia.org/app/dashboards#/view/AXFV7JE83bOlOASGccsT?_g=(time:(from:now-30d,to:now))&_a=(query:(query_string:(query:'normalized_message:%22%5B%7BreqId%7D%5D%20%7Bexception_url%7D%20%20%20PHP%20Notice:%20Undefined%20index:%20tp:tag%22'))) | Find normalized_message in Logstash ]]
```name=normalized_message
[{reqId}] {exception_url} PHP Notice: Undefined index: tp:tag
```
```name=exception.trace,lines=10
from /srv/mediawiki/php-1.37.0-wmf.19/extensions/Translate/src/PageTranslation/PageTranslationSpecialPage.php(490)
#0 /srv/mediawiki/php-1.37.0-wmf.19/extensions/Translate/src/PageTranslation/PageTranslationSpecialPage.php(490): MWExceptionHandler::handleError(integer, string, string, integer, array)
#1 /srv/mediawiki/php-1.37.0-wmf.19/extensions/Translate/src/PageTranslation/PageTranslationSpecialPage.php(524): MediaWiki\Extension\Translate\PageTranslation\PageTranslationSpecialPage->classifyPages(array)
#2 /srv/mediawiki/php-1.37.0-wmf.19/extensions/Translate/src/PageTranslation/PageTranslationSpecialPage.php(110): MediaWiki\Extension\Translate\PageTranslation\PageTranslationSpecialPage->listPages()
#3 /srv/mediawiki/php-1.37.0-wmf.19/includes/specialpage/SpecialPage.php(646): MediaWiki\Extension\Translate\PageTranslation\PageTranslationSpecialPage->execute(NULL)
#4 /srv/mediawiki/php-1.37.0-wmf.19/includes/specialpage/SpecialPageFactory.php(1365): SpecialPage->run(NULL)
#5 /srv/mediawiki/php-1.37.0-wmf.19/includes/MediaWiki.php(314): MediaWiki\SpecialPage\SpecialPageFactory->executePath(string, RequestContext)
#6 /srv/mediawiki/php-1.37.0-wmf.19/includes/MediaWiki.php(925): MediaWiki->performRequest()
#7 /srv/mediawiki/php-1.37.0-wmf.19/includes/MediaWiki.php(559): MediaWiki->main()
#8 /srv/mediawiki/php-1.37.0-wmf.19/index.php(53): MediaWiki->run()
#9 /srv/mediawiki/php-1.37.0-wmf.19/index.php(46): wfIndexMain()
#10 /srv/mediawiki/w/index.php(3): require(string)
#11 {main}
```
==== Notes ====
Started happening 2021/08/20. Low frequency but persistent.