Spotted in **production** with details as follows:
**Error message:**
`[Wsd5nQpAICkAACuB7V0AAAAA] 2018-04-06 13:43:57: Fatal exception of type "Wikimedia\Assert\ParameterTypeException"`
**URL**
`https://www.wikidata.org/w/index.php?title=Special%3AItemByTitle&site=enwiki&page=Categor%C3%ADa%3AProtecci%C3%B3n+de+datos`
**Stacktrace:**
```
Bad value for parameter $pageTitle: must be a string
#0 /srv/mediawiki/php-1.31.0-wmf.28/extensions/Wikibase/lib/includes/Store/Sql/SiteLinkTable.php(216): Wikimedia\Assert\Assert::parameterType(string, boolean, string)
#1 /srv/mediawiki/php-1.31.0-wmf.28/extensions/Wikibase/repo/includes/Specials/SpecialItemByTitle.php(125): Wikibase\Lib\Store\Sql\SiteLinkTable->getItemIdForLink(string, boolean)
#2 /srv/mediawiki/php-1.31.0-wmf.28/includes/specialpage/SpecialPage.php(522): Wikibase\Repo\Specials\SpecialItemByTitle->execute(string)
#3 /srv/mediawiki/php-1.31.0-wmf.28/includes/specialpage/SpecialPageFactory.php(568): SpecialPage->run(string)
#4 /srv/mediawiki/php-1.31.0-wmf.28/includes/MediaWiki.php(288): SpecialPageFactory::executePath(Title, RequestContext)
#5 /srv/mediawiki/php-1.31.0-wmf.28/includes/MediaWiki.php(861): MediaWiki->performRequest()
#6 /srv/mediawiki/php-1.31.0-wmf.28/includes/MediaWiki.php(524): MediaWiki->main()
#7 /srv/mediawiki/php-1.31.0-wmf.28/index.php(42): MediaWiki->run()
#8 /srv/mediawiki/w/index.php(3): include(string)
#9 {main}
```