Add fix for AutoMapping null complex types

Author: mythz

src/ServiceStack.Text/AutoMappingUtils.cs

@@ -734,8 +734,11 @@ public static PropertyGetterDelegate CreateTypeConverter(Type fromType, Type toT
             }
             else
             {
-                return fromValue =>
+                return fromValue => 
                 {
+                    if (fromValue == null) 
+                        return fromValue;
+
                     var toValue = toType.CreateInstance();
                     toValue.PopulateWith(fromValue);
                     return toValue;

tests/ServiceStack.Text.Tests/AutoMappingTests.cs

@@ -408,7 +408,8 @@ public bool MatchesUsers(IEnumerable<User> u1s, IEnumerable<User> u2s)
         [Test]
         public void Does_convert_models_with_collections()
         {
-            var from = new ModelWithEnumerable {
+            var from = new ModelWithEnumerable
+            {
                 Collection = new[] {
                     new User { FirstName = "First1", LastName = "Last1", Car = new Car { Name = "Car1", Age = 1} },
                     new User { FirstName = "First2", LastName = "Last2", Car = new Car { Name = "Car2", Age = 2} },
@@ -437,5 +438,45 @@ public void Does_convert_models_with_collections()
             Assert.That(MatchesUsers(hashset, from.Collection.ConvertTo<User[]>()));
             Assert.That(MatchesUsers(hashset, from.Collection.ConvertTo<HashSet<User>>()));
         }
+
+
+        public class Customer
+        {
+            public CompanyInfo CompanyInfo { get; set; }
+            // other properties
+        }
+
+        public class CustomerDto
+        {
+            public CompanyInfoDto CompanyInfo { get; set; }
+        }
+
+        public class CompanyInfo
+        {
+            public int Id { get; set; }
+            public string ITN { get; set; }
+        }
+
+        public class CompanyInfoDto
+        {
+            public int Id { get; set; }
+            public string ITN { get; set; }
+        }
+
+        [Test]
+        public void Does_retain_null_properties()
+        {
+            var user = new User { FirstName = "Foo" };
+            var userDto = user.ConvertTo<UserFields>();
+
+            Assert.That(userDto.FirstName, Is.EqualTo("Foo"));
+            Assert.That(userDto.LastName, Is.Null);
+            Assert.That(userDto.Car, Is.Null);
+
+            var customer = new Customer { CompanyInfo = null };
+            var dto = customer.ConvertTo<CustomerDto>();
+
+            Assert.That(dto.CompanyInfo, Is.Null);
+        }
     }
 }