don't try create instnce of abstract type

Author: mythz

src/ServiceStack.Text/AutoMappingUtils.cs

@@ -475,6 +475,9 @@ public static object CreateDefaultValue(Type type, Dictionary<Type, int> recursi
 #endif
             }
 
+            if (type.IsAbstract())
+                return null;
+
             // If we have hit our recursion limit for this type, then return null
             int recurseLevel; // will get set to 0 if TryGetValue() fails
             recursionInfo.TryGetValue(type, out recurseLevel);

tests/ServiceStack.Text.Tests/AutoMappingTests.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Linq.Expressions;
 using System.Runtime.Serialization;
@@ -8,6 +9,7 @@
 #endif
 using NUnit.Framework;
 using ServiceStack.Text.Tests.DynamicModels;
+using ServiceStack.Web;
 
 namespace ServiceStack.Text.Tests
 {
@@ -692,5 +694,19 @@ public void Can_call_object_setter_Expressions()
             fn(test, "Foo");
             Assert.That(test.Name, Is.EqualTo("Foo"));
         }
+
+        public class RawRequest : IRequiresRequestStream
+        {
+            public Stream RequestStream { get; set; }
+        }
+
+        [Test]
+        public void Can_create_DTO_with_Stream()
+        {
+            var o = typeof(RawRequest).CreateInstance();
+            var requestObj = AutoMappingUtils.PopulateWith(o);
+
+            Assert.That(requestObj, Is.Not.Null);
+        }
     }
 }