Исправить JsonReaderException (#838)

* Исправить JsonReaderException

* Тест PrettyPrintJson

VkNet.Tests/Utils/UtilitiesTests.cs

@@ -51,5 +51,13 @@ public void JsonConvertWrite()
 			var attribute = Attribute.GetCustomAttribute(typeof(VkCollection<>), typeof(DataContractAttribute));
 			Assert.That(attribute, Is.Null);
 		}
+
+		[Test]
+		public void PrettyPrintJsonShouldNotThrowException()
+		{
+			const string invalidJson = "ERROR";
+
+			Assert.DoesNotThrow(() => Utilities.PrettyPrintJson(invalidJson));
+		}
 	}
 }

VkNet/Utils/Utilities.cs

@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;
 using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
 
 namespace VkNet.Utils
 {
@@ -97,16 +97,13 @@ public static IEnumerable<T> Convert<T>(this VkResponseArray response, Func<VkRe
 		/// <returns> Json </returns>
 		public static string PrettyPrintJson(string json)
 		{
-			using (var stringReader = new StringReader(json))
+			try
 			{
-				using (var stringWriter = new StringWriter())
-				{
-					var jsonReader = new JsonTextReader(stringReader);
-					var jsonWriter = new JsonTextWriter(stringWriter) { Formatting = Formatting.Indented };
-					jsonWriter.WriteToken(jsonReader);
-
-					return stringWriter.ToString();
-				}
+				return JToken.Parse(json).ToString(Formatting.Indented);
+			}
+			catch (JsonReaderException)
+			{
+				return json;
 			}
 		}