I am getting the following error while creating variant.

    ERROR EPiServer.Global: Unhandled exception in ASP.NET
System.Data.NoNullAllowedException: Column 'ClassTypeId' does not allow nulls.
at System.Data.DataColumn.CheckNullable(DataRow row)
at System.Data.DataTable.RaiseRowChanging(DataRowChangeEventArgs args, DataRow eRow, DataRowAction eAction, Boolean fireEvent)
at System.Data.DataTable.SetNewRecordWorker(DataRow row, Int32 proposedRecord, DataRowAction action, Boolean isInMerge, Boolean suppressEnsurePropertyChanged, Int32 position, Boolean fireEvent, Exception& deferredException)
at System.Data.DataTable.InsertRow(DataRow row, Int64 proposedID, Int32 pos, Boolean fireEvent)
at EPiServer.Commerce.Catalog.Provider.Persistence.EntryContentBaseCommitter.CreateEntryRow(EntryContentBase content, ParentsInfo parentInfo)
at EPiServer.Commerce.Catalog.Provider.Persistence.EntryContentBaseCommitter.CreateNew(EntryContentBase content, Boolean syncDraft)
at EPiServer.Commerce.Catalog.Provider.Persistence.EntryContentBaseCommitter.Save(CatalogContentBase content, Boolean syncDraft)
at EPiServer.Commerce.Catalog.Provider.CatalogContentCommitterHandler.SaveVersionInternal(CatalogContentBase content, SaveAction action, String currentUser)
at EPiServer.Commerce.Catalog.Provider.CatalogContentCommitterHandler.Save(CatalogContentBase content, SaveAction action, String currentUser)
at EPiServer.Commerce.Catalog.Provider.CatalogContentProvider.Save(IContent content, SaveAction action)
at EPiServer.Core.Internal.DefaultContentRepository.Save(IContent content, SaveAction action, AccessLevel access)
at EPiServer.Cms.Shell.Service.Internal.ContentService.Save(IContent content, SaveAction saveAction, AccessLevel accessLevel)
at EPiServer.Cms.Shell.Service.Internal.ContentService.Save(IContent content, SaveAction saveAction)
at EPiServer.Cms.Shell.UI.Rest.ContentChangeManager.CreateContent(ContentReference parentLink, Int32 contentTypeId, Nullable`1 resourceFolderId, Boolean createAsLocalAsset, String name, IDictionary`2 properties, SaveAction saveAction)
at EPiServer.Cms.Shell.UI.Rest.ContentChangeManager.Create(ContentReference parentLink, Int32 contentTypeId, Nullable`1 resourceFolderId, Boolean createAsLocalAsset, String name, IDictionary`2 properties, Boolean autoPublish)
at EPiServer.Cms.Shell.UI.Rest.Internal.ContentDataStore.Post(PostContentModel entity)
at lambda_method(Closure , ControllerBase , Object[] )
at System.Web.Mvc.ActionMethodDispatcher.Execute(ControllerBase controller, Object[] parameters)
at System.Web.Mvc.ReflectedActionDescriptor.Execute(ControllerContext controllerContext, IDictionary`2 parameters)
at System.Web.Mvc.ControllerActionInvoker.InvokeActionMethod(ControllerContext controllerContext, ActionDescriptor actionDescriptor, IDictionary`2 parameters)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c.<BeginInvokeSynchronousActionMethod>b__9_0(IAsyncResult asyncResult, ActionInvocation innerInvokeState)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`2.CallEndDelegate(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethod(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_0.<InvokeActionMethodFilterAsynchronouslyRecursive>b__0()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.AsyncInvocationWithFilters.<>c__DisplayClass11_2.<InvokeActionMethodFilterAsynchronouslyRecursive>b__2()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass7_0.<BeginInvokeActionMethodWithFilters>b__1(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeActionMethodWithFilters(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_6.<BeginInvokeAction>b__4()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.<>c__DisplayClass3_1.<BeginInvokeAction>b__1(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResult`1.CallEndDelegate(IAsyncResult asyncResult)
at System.Web.Mvc.Async.AsyncResultWrapper.WrappedAsyncResultBase`1.End()
at System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult)
at EPiServer.Shell.Services.Rest.RestControllerBase.EndExecute(IAsyncResult asyncResult)
at EPiServer.Shell.Services.Rest.RestHttpHandler.EndProcessRequest(IAsyncResult result)
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)