Update Index.cshtml

Fix for:
ExceptionMessage: "Object reference not set to an instance of an object."
ExceptionType: "System.NullReferenceException"
Message: "An error has occurred."
StackTrace: "   at HawkNet.HttpRequestMessageExtensions.<AuthenticateAsync>d__7.MoveNext()
?--- End of stack trace from previous location where exception was thrown ---
?   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
?   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
?   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
?   at HawkNet.WebApi.HawkMessageHandler.<SendAsync>d__0.MoveNext()
?--- End of stack trace from previous location where exception was thrown ---
?   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
?   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
?   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
?   at System.Web.Http.Cors.CorsMessageHandler.<SendAsync>d__0.MoveNext()
?--- End of stack trace from previous location where exception was thrown ---
?   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
?   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
?   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
?   at System.Web.Http.HttpServer.<SendAsync>d__0.MoveNext()"