I've deleted a doctype in umbraco 7.1.4 and now I cannot get content in tree- I get this error msg Server error: Contact administrator, see log for full details.Failed to retrieve data for application tree content

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{"Message":"An error has occurred.","ExceptionMessage":"Value cannot be null.\r\nParameter name: contentType","ExceptionType":"System.ArgumentNullException","StackTrace":"   at Umbraco.Core.Mandate.That[TException](Boolean condition, Func`1 defer)\r\n   at Umbraco.Core.Models.ContentBase..ctor(String name, Int32 parentId, IContentTypeComposition contentType, PropertyCollection properties)\r\n   at Umbraco.Core.Models.Content..ctor(String name, Int32 parentId, IContentType contentType, PropertyCollection properties)\r\n   at Umbraco.Core.Models.Content..ctor(String name, Int32 parentId, IContentType contentType)\r\n   at Umbraco.Core.Persistence.Factories.ContentFactory.BuildEntity(DocumentDto dto)\r\n   at Umbraco.Core.Persistence.Repositories.ContentRepository.CreateContentFromDto(DocumentDto dto, Guid versionId)\r\n   at Umbraco.Core.Persistence.Repositories.ContentRepository.PerformGet(Int32 id)\r\n   at Umbraco.Core.Persistence.Repositories.RepositoryBase`2.Get(TId id)\r\n   at Umbraco.Core.Persistence.Repositories.ContentRepository.d__24.MoveNext()\r\n   at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()\r\n   at System.Linq.Enumerable.Any[TSource](IEnumerable`1 source)\r\n   at Umbraco.Web.Trees.ContentTreeControllerBase.GetTreeNodes(String id, FormDataCollection queryStrings)\r\n   at Umbraco.Web.Trees.TreeControllerBase.GetNodes(String id, FormDataCollection queryStrings)\r\n   at Umbraco.Web.Trees.ApplicationTreeExtensions.TryLoadFromControllerTree(ApplicationTree appTree, String id, FormDataCollection formCollection, HttpControllerContext controllerContext)\r\n   at Umbraco.Web.Trees.ApplicationTreeController.d__17.MoveNext()\r\n--- End of stack trace from previous location where exception was thrown ---\r\n   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\r\n   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()\r\n   at Umbraco.Web.Trees.ApplicationTreeController.d__4.MoveNext()"}