Default Error Message in ReportViewer

I am working with ReportViewer (SP and DataSet) in ASP.SET which works fine and showing data. But when The report initially uploads There is a default error message like This:
'An error occurred during local report processing. The report definition for report 'Report9' has not been specified Object reference not set to an instance of an object'. How can I remove This message Though IT doesn't create any problem?? My code is as follow:

 protected void Page_Load(object sender, EventArgs e) // To select data which is To be printed in The report         {             using (var context = new SMPURCHASEEntities())             {      & ...