AjaxControlToolkit and LineChart control doesn't work on IE8

Hello,

I'm using the LineChart Control with AjaxControlToolkit version 4.1.7.123 with ASP.NET framework 4.0

So my problem is : In Chrome, Firefox and IE11, my chart is displayed but for IE8, I have an error on my page :

URI : http://outil-performance.azurewebsites.net/Stats_alertes.aspx?_TSM_HiddenField_=ToolkitScriptManager1_HiddenField&_TSM_CombinedScripts_=%3b%3bAjaxControlToolkit%2c+Version%3d4.1.7.123%2c+Culture%3dneutral%2c+PublicKeyToken%3d28f01b0e84b6d53e%3aen-US%3a57898466-f347-4e5c-9527-24f201596811%3ade1feab2%3af9cec9bc%3a9fd3e5ca

Do you have a solution ?