Server Error in '/' Application. Object reference not set to an instance of an object.

Server Error in '/' Application. Object reference not set to an instance of an object. 

Issue: while accessing the SharePoint 2013 site we get the error below.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.  

Stack Trace: [NullReferenceException: Object reference not set to an instance of an object.]   Microsoft.SharePoint.Utilities.SPUtility.RedirectToAccessDeniedPage(HttpContext context) +66   Microsoft.SharePoint.Utilities.SPUtility.HandleAccessDenied(HttpContext context) +759   Microsoft.SharePoint.IdentityModel.SPFederationAuthenticationModule.OnEndRequest(Object sender, EventArgs eventArgs) +1197   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +181   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +164

 Solution: Please follow the below steps to resolve the issue.

1.   Ensure the Root site(/) is created for the web application.

                                            
                                               


                                                

                                               

I hope the above information will help you to resolve the issue, in case of any queries/questions regarding the above mentioned information then please let me know. I would be more than happy to help you as well as resolves your issues, Thank you.