Added one additional test to cover both self and related links being null

Author: sarus

test/serializer.js

@@ -2662,6 +2662,33 @@ describe('JSON API Serializer', function () {
       expect(json.data.relationships.address).eql({ data: null });
     });
 
+    it('should not be set when the self and related relationshipLinks return null', function () {
+      var dataSet = {
+        id: '54735750e16638ba1eee59cb',
+        firstName: 'Sandro',
+        lastName: 'Munda',
+        address: null,
+      };
+
+      var json = new JSONAPISerializer('users', {
+        attributes: ['firstName', 'lastName', 'address'],
+        address: {
+          ref: 'id',
+          included: false,
+          relationshipLinks: {
+            self: function () {
+              return null;
+            },
+            related: function(){
+              return null;
+            }
+          },
+        }
+      }).serialize(dataSet);
+
+      expect(json.data.relationships.address).eql({ data: null });
+    });
+
     it('should be set when the relationshipLinks returns a self link only', function () {
       var dataSet = {
         id: '54735750e16638ba1eee59cb',