fix(ng:repeat): support repeating over array with null

typeof null == 'object', but it doesn't behave like an object
because its properties can't be dereferenced, so we need
to special-case it.

Closes #702

test/widgetsSpec.js

@@ -501,6 +501,14 @@ describe('widget', function() {
       expect(element.text()).toBe('a|b|||c||d|');
     }));
 
+    it('should iterate over all kinds of types', inject(function($rootScope, $compile) {
+      var element = $compile('<ul><li ng:repeat="item in array">{{item}}|</li></ul>')($rootScope);
+      $rootScope.array = ['a', 1, null, undefined, {}];
+      $rootScope.$digest();
+
+      expect(element.text()).toBe('a|1|||{\n  }|');
+    }));
+
 
     it('should iterate over all kinds of types', inject(function($rootScope, $compile) {
       var element = $compile('<ul><li ng:repeat="item in array">{{item}}|</li></ul>')($rootScope);