environment: Fix transition callback

This is rather embarrassing - we currently confuse the transition with
the finished parameter, which means we always run the onComplete handler
no matter whether the transition was interrupted or actually completed.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/668

js/ui/environment.js

@@ -64,7 +64,7 @@ function _trackTransition(transition, callback) {
     if (_easingTransitions.has(transition))
         transition.disconnect(_easingTransitions.get(transition));
 
-    let id = transition.connect('stopped', isFinished => {
+    let id = transition.connect('stopped', (t, isFinished) => {
         _easingTransitions.delete(transition);
         callback(isFinished);
     });