ImageServing: Thumbnail image not appearing in latest news articles

@Wikia/platform-team

This regression was caused by PLATFORM-285. Video (or any other image) that was used only on a single blog post (i.e. outside content namespace) was not added to the list of images with popularity score (calculated only for images used on content namespaces) and as a result not added to the list of images suggested for a given article.

PLATFORM-358
Ah, sorry, I didn't realize where this was. The overarching issue prompted this PR https://github.com/Wikia/app/pull/4345.