fix(ngMock): return false from mock $interval.cancel() when no argument is supplied

Closes #6103.
Closed #6099.

Author: dluxemburg

src/ngMock/angular-mocks.js

@@ -504,6 +504,7 @@ angular.mock.$IntervalProvider = function() {
     };
 
     $interval.cancel = function(promise) {
+      if(!promise) return false;
       var fnIndex;
 
       angular.forEach(repeatFns, function(fn, index) {

test/ngMock/angular-mocksSpec.js

@@ -509,6 +509,11 @@ describe('ngMock', function() {
 
       it('should not throw a runtime exception when given an undefined promise',
           inject(function($interval) {
+        var task1 = jasmine.createSpy('task1'),
+            promise1;
+
+        promise1 = $interval(task1, 1000, 1);
+
         expect($interval.cancel()).toBe(false);
       }));
     });