ibusCandidatePopup: Fix cursor positioning

After moving the dummy source actor, we still have to poke the
boxpointer so that it gets repositioned.

This has always been broken but went unnoticed until now since none of
the commonly used engines currently depend on this method. Thanks to
Mathieu Bridon for pointing it out.

https://bugzilla.gnome.org/show_bug.cgi?id=691902

js/ui/ibusCandidatePopup.js

@@ -159,6 +159,8 @@ const CandidatePopup = new Lang.Class({
                              Lang.bind(this, function(ps, x, y, w, h) {
                                  this._cursor.set_position(x, y);
                                  this._cursor.set_size(w, h);
+                                 if (this._boxPointer.actor.visible)
+                                     this._boxPointer.setPosition(this._cursor, 0);
                              }));
         panelService.connect('update-preedit-text',
                              Lang.bind(this, function(ps, text, cursorPosition, visible) {