This fixes an NPE when an action is declared by the server but there
is no client side JS supplied. The $wnd.Gerrit.change_actions map
must still be defined to allow the client side to identify there is no
JavaScript to execute before the REST API call.
Change-Id: I3d3cccf91f61305279f1480716fbb58a0a13794d
a6946b5a54