Middle-click not working

[leehart]

E.g.
Samples_and_Variants > Start page
Middle-click on the "Page of examples" DocLink, which should open the DocPage in a new tab.
Nothing happens.
It looks like the click handler in DocLink (handleClick(e)) isn't even being called.

[benjeffery]

This is also a wider issue - for example middle clicking a post in a <Feed/>