I've just installed the most recent version of Phabricator (0b4ed94cc6ad6ff58d058f43ccce8259174fed18), imported a repository and opened a file in Diffusion and clicked on „Disable Highlighting“.
It caused a Unhandled Exception ("Exception"):

Bad getter call: getShortName

Whenever I try to view a file in Diffusion now, I get this error message.