Lots of this error showing up in logstash: 12,721 errors in the last 12 hours, triggering alerting system.
TypeError: Cannot read property 'top' of undefined
https://logstash.wikimedia.org/goto/545fd39842e3c16cfa78a0bd057b652f
All are on mobile sites. Most of the stack traces look like this, so it looks like something to do with RelatedArticles
at Object.isElementInViewport <anonymous>:231:41753 at Object.isElementCloseToViewport <anonymous>:232:54 at loadRelatedArticles <anonymous>:103:7018 at HTMLDocument.showReadMore <anonymous>:104:36 at mightThrow https://fr.m.wikipedia.org/w/load.php?lang=fr&modules=jquery%2Coojs-ui-core%2Coojs-ui-widgets&skin=minerva&version=udccx:49:833 at process https://fr.m.wikipedia.org/w/load.php?lang=fr&modules=jquery%2Coojs-ui-core%2Coojs-ui-widgets&skin=minerva&version=udccx:50:498