System.NullReferenceException: Object reference not set to an instance of an object.
   at DocumentManagement.MediatR.Handlers.UpdateDocumentCommandHandler.Handle(UpdateDocumentCommand request, CancellationToken cancellationToken) in D:\Projects\Client\AMPLUSNET\docs-api\DocumentManagement.MediatR\Handlers\Document\UpdateDocumentCommandHandler.cs:line 76
   at DocumentManagement.MediatR.ValidationBehavior`2.Handle(TRequest request, RequestHandlerDelegate`1 next, CancellationToken cancellationToken) in D:\Projects\Client\AMPLUSNET\docs-api\DocumentManagement.MediatR\PipeLineBehavior\ValidationBehavior.cs:line 43
   at MediatR.Pipeline.RequestExceptionProcessorBehavior`2.Handle(TRequest request, RequestHandlerDelegate`1 next, CancellationToken cancellationToken)
   at MediatR.Pipeline.RequestExceptionProcessorBehavior`2.Handle(TRequest request, RequestHandlerDelegate`1 next, CancellationToken cancellationToken)
   at MediatR.Pipeline.RequestExceptionActionProcessorBehavior`2.Handle(TRequest request, RequestHandlerDelegate`1 next, CancellationToken cancellationToken)
   at MediatR.Pipeline.RequestExceptionActionProcessorBehavior`2.Handle(TRequest request, RequestHandlerDelegate`1 next, CancellationToken cancellationToken)
   at MediatR.Pipeline.RequestPostProcessorBehavior`2.Handle(TRequest request, RequestHandlerDelegate`1 next, CancellationToken cancellationToken)
   at MediatR.Pipeline.RequestPreProcessorBehavior`2.Handle(TRequest request, RequestHandlerDelegate`1 next, CancellationToken cancellationToken)
   at DocumentManagement.API.Controllers.DocumentController.UpdateDocument(Guid Id, UpdateDocumentCommand updateDocumentCommand) in D:\Projects\Client\AMPLUSNET\docs-api\DocumentManagement.API\Controllers\Document\DocumentController.cs:line 150
   at Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor.TaskOfIActionResultExecutor.Execute(ActionContext actionContext, IActionResultTypeMapper mapper, ObjectMethodExecutor executor, Object controller, Object[] arguments)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Awaited|12_0(ControllerActionInvoker invoker, ValueTask`1 actionResultValueTask)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeFilterPipelineAsync>g__Awaited|20_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at Microsoft.AspNetCore.ResponseCompression.ResponseCompressionMiddleware.InvokeCore(HttpContext context)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
   at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)