An unhandled exception has occurred while executing the request

Questions
1

I got this error how can i solve this

System.InvalidOperationException: Could not obtain an IUser instance from IPrincipal
   at Umbraco.Cms.Core.Security.Authorization.AuthorizationHelper.GetUmbracoUser(IPrincipal currentUser)
   at Umbraco.Cms.Api.Management.Security.Authorization.User.AllowedApplicationHandler.IsAuthorized(AuthorizationHandlerContext context, AllowedApplicationRequirement requirement)
   at Umbraco.Cms.Api.Management.Security.Authorization.MustSatisfyRequirementAuthorizationHandler`1.HandleRequirementAsync(AuthorizationHandlerContext context, T requirement)
   at Microsoft.AspNetCore.Authorization.AuthorizationHandler`1.HandleAsync(AuthorizationHandlerContext context)
   at Microsoft.AspNetCore.Authorization.DefaultAuthorizationService.AuthorizeAsync(ClaimsPrincipal user, Object resource, IEnumerable`1 requirements)
   at Microsoft.AspNetCore.Authorization.Policy.PolicyEvaluator.AuthorizeAsync(AuthorizationPolicy policy, AuthenticateResult authenticationResult, HttpContext context, Object resource)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at StackExchange.Profiling.MiniProfilerMiddleware.Invoke(HttpContext context) in C:\projects\dotnet\src\MiniProfiler.AspNetCore\MiniProfilerMiddleware.cs:line 112
   at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
   at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
   at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<<CreateMiddleware>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at Umbraco.Cms.Web.Common.Middleware.PreviewAuthenticationMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
   at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<<CreateMiddleware>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestLoggingMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
   at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<<CreateMiddleware>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Diagnostics.ExceptionHandlerMiddlewareImpl.<Invoke>g__Awaited|10_0(ExceptionHandlerMiddlewareImpl middleware, HttpContext context, Task task)
This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/114551-an-unhandled-exception-has-occurred-while-executing-the-request