Don't assume selection is of an item, sometimes it's null
Don't assume selection is of an item, sometimes it's null

Since selectItem() is allowed to accept null, assuming the item argument
of a 'select' event handler is an object is clearly dangerous.

Change-Id: If8eedc7d850f4d978b3b894bdf05da8e32969b07

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui