fix($animateCss): don't unregister when events are empty

src/ngAnimate/animateCss.js

@@ -750,7 +750,7 @@ var $AnimateCssProvider = ['$animateProvider', function($animateProvider) {
         }
 
         // Remove the transitionend / animationend listener(s)
-        if (events) {
+        if (events && events.length) {
           element.off(events.join(' '), onAnimationProgress);
         }
 

test/ngAnimate/animateCssSpec.js

@@ -1502,6 +1502,37 @@ describe("ngAnimate $animateCss", function() {
               expect(elementOffSpy.mostRecentCall.args[0]).toBe(event);
             });
         });
+
+        they("should not add or remove $prop event listeners when end() is called before rAF has been triggered",
+          [TRANSITIONEND_EVENT, ANIMATIONEND_EVENT], function(event) {
+            inject(function($animateCss, $timeout) {
+
+              setStyles(event);
+
+              // Make sure other event listeners aren't removed by accident
+              var otherEndSpy = jasmine.createSpy('otherEndSpy');
+              element.on(event, otherEndSpy);
+
+              expect(elementOnSpy).toHaveBeenCalledOnce();
+              elementOnSpy.reset();
+
+              var animator = $animateCss(element, {
+                event: 'enter',
+                structural: true
+              });
+
+              var runner = animator.start();
+              expect(elementOnSpy).not.toHaveBeenCalled();
+
+              // This closes the animation before it has started
+              runner.end();
+              expect(elementOffSpy).not.toHaveBeenCalled();
+
+              progress(element, 10);
+              expect(otherEndSpy).toHaveBeenCalledOnce();
+            });
+        });
+
       });
     });