Steps to replicate the issue (include links if applicable):

• Visit Kategorija:Астрономија and go to its category member.
• Use the Quarry platform to obtain the page ID of its category member: my query for Kategorija:Астрономија
• Try to figure out the correct page name using the page ID: https://sh.wikipedia.org/wiki/index.php?curid=490582

What happens?:

• Razgovor:Категорија:Астрономија appeared as category member and is not a valid page name.
• Fatal error when trying to access the page using page ID:

MediaWiki internal error.

Original exception: [0676078e-4535-4a46-87d8-dfadec18f596] 2024-01-27 14:37:15: Fatal exception of type "Wikimedia\Assert\PostconditionException"

Exception caught inside exception handler.

Set $wgShowExceptionDetails = true; at the bottom of LocalSettings.php to show detailed debugging information.

What should have happened instead?:

No such invalid category member, no fatal exceptions.

Software version (skip for WMF-hosted wikis like Wikipedia):

Other information (browser name/version, screenshots, etc.):

• The page table entry for page_id = 490582: namespace=1, title=Категорија:Астрономија (https://quarry.wmcloud.org/query/79988)
• The revision table entry for page_id = 490582: revid=2326387, timestamp=20140309030534 (https://quarry.wmcloud.org/query/79990)

Original report

In T329469#9492159, @Winston_Sung wrote:

On 2024-01-27 13:13 (UTC), Aca wrote:

Edgar and I found some pretty strange categories on sh.WP, and we think they might be related to LanguageConverter or some of the patches deployed earlier.

They can be found on the last page of Wanted categories special page.

Specifically, I'm referring to:

• https://sh.wikipedia.org/wiki/Kategorija:Астрономија
• https://sh.wikipedia.org/wiki/Kategorija:Астрофизика
• https://sh.wikipedia.org/wiki/Kategorija:Земља
• https://sh.wikipedia.org/wiki/Kategorija:Наука_о_планетама
• https://sh.wikipedia.org/wiki/Kategorija:Планете
• https://sh.wikipedia.org/wiki/Kategorija:Сунчев_систем

Seems like they are populated by pages that don't exist (?)