Uncaught TypeError: Cannot read property 'off' of null
at HTMLAnchorElement.mw.popups.render.leaveInactive (eval at <anonymous> (https://www.mediawiki.org/w/load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0f3xo9s:1:1), <anonymous>:33:466)
at HTMLAnchorElement.handle (https://www.mediawiki.org/w/load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0f3xo9s:71:556)
at HTMLAnchorElement.dispatch (https://www.mediawiki.org/w/load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0f3xo9s:65:986)
at HTMLAnchorElement.elemData.handle (https://www.mediawiki.org/w/load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=0f3xo9s:60:481)I see this error quite often on mediawiki.org when interacting with links in a way that would make Hovercards change state (e.g. mouseover, mouseout). Sometimes it happens when changing browser windows or tabs via the keyboard. Sometimes it gets into an infinite cycle (that's probably partly due to my user script changing Javascript errors into alerts - displaying the dialog might re-trigger the error somehow). Usually Hovercards behaves funky afterwards, e.g. it's visible when the mouse is not on the link and disappears when on it, or the card pops up every time I bring up the browser tab via ctrl+tab. I was not able to find a way to reproduce it.