WIP: fix regression pointed out by @lgalfaso

Author: IgorMinar

src/ng/rootScope.js

@@ -756,6 +756,7 @@ function $RootScopeProvider(){
 
         // prevent NPEs since these methods have references to properties we nulled out
         this.$destroy = this.$digest = this.$apply = noop;
+        this.$on = this.$watch = function() { return noop; };
 
 
         /* jshint -W103 */

test/ng/rootScopeSpec.js

@@ -876,6 +876,28 @@ describe('Scope', function() {
       $rootScope.$broadcast(EVENT);
       expect(spy.callCount).toBe(1);
     }));
+
+
+    it("should do nothing when a child event listener is registered after parent's destruction",
+        inject(function($rootScope) {
+      var parent = $rootScope.$new(),
+          child = parent.$new();
+
+      parent.$destroy();
+      var fn = child.$on('someEvent', function() {});
+      expect(fn).toBe(noop);
+    }));
+
+
+    it("should do nothing when a child watch is registered after parent's destruction",
+        inject(function($rootScope) {
+      var parent = $rootScope.$new(),
+          child = parent.$new();
+
+      parent.$destroy();
+      var fn = child.$watch('somePath', function() {});
+      expect(fn).toBe(noop);
+    }));
   });