When opening a commit in Diffusion (with the URL /r<CALLSIGN><COMMIT-HASH>), the following exception is shown:

Unhandled Exception ("PhutilMissingSymbolException")
Failed to load class or interface 'PHUIDiffRevealIconView': the class or interface 'PHUIDiffRevealIconView' is not defined in the library map for any loaded phutil library. If this symbol was recently added or moved, your library map may be out of date. You can rebuild the map by running 'arc liberate'. For more information, see: http://www.phabricator.com/docs/phabricator/article/libphutil_Libraries_User_Guide.html

There is no stacktrace.