The static HttpContext.Current property returns null when the calling-thread is not the same thread that was associated with the current HTTP request/response. (#949)

Add a workaround for it when called from objects with UseBigStack enabled.

Author: claudiamurialdo

dotnet/src/dotnetframework/GxClasses/Middleware/GXHttp.cs

@@ -2281,6 +2281,9 @@ protected virtual void sendSpaHeaders()
 		private void webExecuteWorker(object target)
 		{
 			HttpContext httpContext = (HttpContext)target;
+#if !NETCORE
+			HttpContext.Current = httpContext;
+#endif
 			try
 			{
 				webExecuteEx(httpContext);