fix embedsOne error when embed instance is undefined or null

Signed-off-by: Clark Wang <clark.wangs@gmail.com>

lib/relation-definition.js

@@ -1751,7 +1751,7 @@ RelationDefinition.embedsOne = function (modelFrom, modelTo, params) {
     configurable: true,
     get: function() {
       var relation = new EmbedsOne(definition, this);
-      var relationMethod = relation.related.bind(relation)
+      var relationMethod = relation.related.bind(relation);
       relationMethod.create = relation.create.bind(relation);
       relationMethod.build = relation.build.bind(relation);
       relationMethod.update = relation.update.bind(relation);
@@ -1795,7 +1795,10 @@ EmbedsOne.prototype.related = function (refresh, params) {
   }
   
   var embeddedInstance = modelInstance[propertyName];
-  embeddedInstance.__persisted = true;
+
+  if (embeddedInstance) {
+    embeddedInstance.__persisted = true;
+  }
   
   if (typeof params === 'function') { // acts as async getter
     var cb = params;

test/relations.test.js

@@ -2011,6 +2011,7 @@ describe('relations', function () {
   describe('embedsOne', function () {
     
     var person;
+    var Passport;
     var Other;
     
     before(function () {
@@ -2021,6 +2022,7 @@ describe('relations', function () {
         {name:{type:'string', required: true}}, 
         {idInjection: false}
       );
+      Address = tmp.define('Address', { street: String }, { idInjection: false });
       Other = db.define('Other', {name: String});
     });
 
@@ -2028,6 +2030,7 @@ describe('relations', function () {
       Person.embedsOne(Passport, {
         default: {name: 'Anonymous'} // a bit contrived
       });
+      Person.embedsOne(Address); // all by default
       db.automigrate(done);
     });
     
@@ -2039,6 +2042,19 @@ describe('relations', function () {
       p.passportItem.build.should.be.a.function;
       p.passportItem.destroy.should.be.a.function;
     });
+
+    it('should behave properly without default or being set', function (done) {
+      var p = new Person();
+      should.not.exist(p.address);
+      var a = p.addressItem();
+      should.not.exist(a);
+      Person.create({}, function (err, p) {
+        should.not.exist(p.address);
+        var a = p.addressItem();
+        should.not.exist(a);
+        done();
+      });
+    });
     
     it('should return an instance with default values', function() {
       var p = new Person();