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Cannot read property 'off' of null
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Description

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.

Event Timeline

Tgr created this task.Oct 24 2016, 3:03 AM
Restricted Application added a subscriber: Aklapper. · View Herald TranscriptOct 24 2016, 3:03 AM
bmansurov moved this task from Incoming to Needs Prioritization on the Readers-Web-Backlog board.
bmansurov added a subscriber: bmansurov.

Let's add clear steps to reproduce the issue: some links to pages where this is happening, affected browsers, etc.

Tgr added a comment.Oct 26 2016, 9:23 PM

Chrome 54.0.2840.71 / Ubuntu 16.04, any mediawiki.org page with links. I see this error a couple times a day (but then I use mw.org a lot).

Tgr added a comment.Oct 27 2016, 10:12 PM

One methods that seems reproducible with some luck is middle-clicking on a link just about the same time when the popup for the link shows up.

ovasileva changed the task status from Open to Stalled.Nov 2 2016, 8:06 PM