Double uppercase issue

src/RestSharp/Serializers/Json/JsonSerializer.cs

@@ -120,7 +120,7 @@ object Map(object target, IDictionary<string, object> data)
                 if (!data.TryGetValue(name, out var value))
                 {
                     var parts       = name.Split('.');
-                    var currentData = data;
+                    IDictionary<string, object> currentData = new Dictionary<string, object>(data, StringComparer.Create(Culture, true));
 
                     for (var i = 0; i < parts.Length; ++i)
                     {

test/RestSharp.Tests/JsonTests.cs

@@ -436,6 +436,17 @@ public void Can_Deserialize_Lists_of_Simple_Types()
             Assert.IsNotEmpty(output.Numbers);
         }
 
+        [Test]
+        public void Can_Deserialize_Names_With_Double_Uppercase()
+        {
+            var doc = JsonData.CreateJsonWithDoubleUppercase();
+            var serializer = new JsonSerializer();
+            var response = new RestResponse { Content = doc };
+            var p = serializer.Deserialize<PersonForJson>(response);
+
+            Assert.AreEqual(435, p.PersonId);
+        }
+
         [Test]
         public void Can_Deserialize_Names_With_Dashes_With_Default_Root()
         {

test/RestSharp.Tests/SampleClasses/misc.cs

@@ -127,6 +127,8 @@ public class PersonForJson
         public Order Order { get; set; }
 
         public Disposition Disposition { get; set; }
+
+        public int PersonId { get; set; }
     }
 
     public enum Order { First, Second, Third }

test/RestSharp.Tests/TestData/JsonData.cs

@@ -126,6 +126,15 @@ public static string CreateJsonWithDashes()
             return doc.ToString();
         }
 
+        public static string CreateJsonWithDoubleUppercase()
+        {
+            var doc = new JsonObject
+            {
+                ["personID"] = 435,
+            };
+            return doc.ToString();
+        }
+
         public static string CreateJson()
         {
             var doc = new JsonObject