-Fixed empty string being changed to null on object properties

Src/Newtonsoft.Json.Tests/Serialization/JsonSerializerTest.cs

@@ -5286,6 +5286,18 @@ keyword such as type of business.""
 
       Assert.AreEqual(new WidgetId1 { Value = 1234 }, w.Id);
     }
+
+    [Test]
+    public void SerializeDictionaryStringStringAndStringObject()
+    {
+      var serializer = JsonSerializer.Create(new JsonSerializerSettings());
+      var dict = serializer.Deserialize<Dictionary<string, string>>(new JsonTextReader(new StringReader("{'k1':'','k2':'v2'}")));
+
+      var reader = new JsonTextReader(new StringReader("{'k1':'','k2':'v2'}"));
+      var dict2 = serializer.Deserialize<Dictionary<string, object>>(reader);
+
+      Assert.AreEqual(dict["k1"], dict2["k1"]);
+    } 
   }
 
   public class Widget1

Src/Newtonsoft.Json/Serialization/JsonSerializerInternalReader.cs

@@ -244,7 +244,7 @@ namespace Newtonsoft.Json.Serialization
             return EnsureType(reader, reader.Value, CultureInfo.InvariantCulture, contract, objectType);
           case JsonToken.String:
             // convert empty string to null automatically for nullable types
-            if (string.IsNullOrEmpty((string) reader.Value) && objectType != typeof(string) && contract.IsNullable)
+            if (string.IsNullOrEmpty((string)reader.Value) && objectType != typeof(string) && objectType != typeof(object) && contract.IsNullable)
               return null;
 
             // string that needs to be returned as a byte array should be base 64 decoded