-Fixed deserializing null Regex

Src/Newtonsoft.Json.Tests/Converters/RegexConverterTests.cs

@@ -232,5 +232,20 @@ namespace Newtonsoft.Json.Tests.Converters
             Assert.AreEqual("", newRegex.Regex.ToString());
             Assert.AreEqual(RegexOptions.None, newRegex.Regex.Options);
         }
+
+        public class SimpleClassWithRegex
+        {
+            public Regex RegProp { get; set; }
+        }
+
+        [Test]
+        public void DeserializeNullRegex()
+        {
+            string json = JsonConvert.SerializeObject(new SimpleClassWithRegex { RegProp = null });
+            Assert.AreEqual(@"{""RegProp"":null}", json);
+
+            SimpleClassWithRegex obj = JsonConvert.DeserializeObject<SimpleClassWithRegex>(json);
+            Assert.AreEqual(null, obj.RegProp);
+        }
     }
 }

Src/Newtonsoft.Json/Converters/RegexConverter.cs

@@ -123,14 +123,14 @@ namespace Newtonsoft.Json.Converters
         /// <returns>The object value.</returns>
         public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
         {
-            if (reader.TokenType == JsonToken.StartObject)
+            switch (reader.TokenType)
             {
-                return ReadRegexObject(reader, serializer);
-            }
-
-            if (reader.TokenType == JsonToken.String)
-            {
-                return ReadRegexString(reader);
+                case JsonToken.StartObject:
+                    return ReadRegexObject(reader, serializer);
+                case JsonToken.String:
+                    return ReadRegexString(reader);
+                case JsonToken.Null:
+                    return null;
             }
 
             throw JsonSerializationException.Create(reader, "Unexpected token when reading Regex.");