Error after Searching E-Mails

I get an error mark beside my account when I seach an e-mail with the text “Die Verbindung ist felhgeschlagen…”

This error does not exist in EM-Client Version 7.x

The protocol shows a NullException:

08:27:43 [email protected] [Exchange Web Services] MailClient.Accounts.ConnectionException: Value cannot be null. (Parameter ‘source’)
—> System.ArgumentNullException: Value cannot be null. (Parameter ‘source’)
at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
at System.Linq.Enumerable.Select[TSource,TResult](IEnumerable1 source, Func2 selector)
at MailClient.Protocols.Exchange.ExchangeMailSynchronizer.<>c__DisplayClass44_0.b__0(WorkerStatus status, CancellationToken cancellationToken)
at MailClient.Protocols.Common.RequestIssuer.<>c__DisplayClass11_01.<RunRequest>b__0(WorkerStatus ws, CancellationToken ct) at MailClient.Protocols.Exchange.ExchangeGenericCommand.Execute(WorkerStatus status) --- End of inner exception stack trace --- at MailClient.Protocols.Exchange.ExchangeGenericCommand.Execute(WorkerStatus status) at MailClient.Commands.Command.Process(WorkerStatus status) --- End of stack trace from previous location --- at MailClient.Storage.Application.Folder.ConvertSearchQuery(QueryCondition query, Folder[] xfolders, IMailSearchSynchronizer synchronizer, CancellationToken cancellationToken) EnqueuedStackTrace = at MailClient.Protocols.Common.RequestIssuer.RunRequest[T](Func3 action, CancellationToken cancellationToken, OperationPriority priority, String errorFormat, Object[] errorParams)
at MailClient.Protocols.Exchange.ExchangeMailSynchronizer.SearchForIdsAsync(IReadOnlyList1 folders, QueryCondition condition, Int32 limit, CancellationToken cancellationToken1) at MailClient.Storage.Application.Folder.ConvertSearchQuery(QueryCondition query, Folder[] xfolders, IMailSearchSynchronizer synchronizer, CancellationToken cancellationToken) at MailClient.Storage.Application.Folder.ConvertSearchQuery(QueryCondition query, Folder[] xfolders, IMailSearchSynchronizer synchronizer, CancellationToken cancellationToken) at MailClient.Storage.Application.Folder.ConvertSearchQuery(QueryCondition query, Folder[] xfolders, IMailSearchSynchronizer synchronizer, CancellationToken cancellationToken) at MailClient.Storage.Application.Folder.ConvertSearchQuery(QueryDefinition query, Folder[] xfolders, IMailSearchSynchronizer synchronizer, CancellationToken cancellationToken) at MailClient.Storage.Application.Folder.UpdateFolderSubjectQuery(Folder folder, CancellationToken cancellationToken) at MailClient.Storage.Application.Folder.CreateMailView(IUIDispatcher dispatcher, CancellationToken cancellationToken, ViewModifiers viewModifiers, SortField[] sortFields) at MailClient.Storage.Application.AggregatedViewProvider.<>c__DisplayClass20_0.<CreateMailView>b__1(Folder f) at System.Linq.Enumerable.SelectArrayIterator2.MoveNext()
at MailClient.Storage.Views.AggregatedCollectionView1..ctor(IUIDispatcher dispatcher, Comparison1 comparer, TBaseItem dummyItem, Boolean ownsViews, IEnumerable1 itemCollectionViews) at MailClient.Storage.Application.AggregatedViewProvider.CreateMailView(IUIDispatcher dispatcher, CancellationToken cancellationToken, ViewModifiers viewModifiers, SortField[] sortFields) at MailClient.UI.Controls.controlMessages.MailItemBehaviour.CreateView(IViewProvider viewProvider, IUIDispatcher dispatcher, CancellationToken cancellationToken, SortField[] sortFields) at MailClient.UI.Controls.controlItemListGeneric2.<>c__DisplayClass194_0.b__0(Object )
at System.Threading.QueueUserWorkItemCallback.<>c.<.cctor>b__6_0(QueueUserWorkItemCallback quwi)
at System.Threading.ExecutionContext.RunForThreadPoolUnsafe[TState](ExecutionContext executionContext, Action`1 callback, TState& state)
at System.Threading.QueueUserWorkItemCallback.Execute()
at System.Threading.ThreadPoolWorkQueue.Dispatch()
at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
GUIStatus_Exception_Reported = True
08:27:43 [email protected] [Exchange Web Services] System.Threading.Tasks.TaskCanceledException: A task was canceled.
at MailClient.Storage.Synchronization.FolderSynchronizerExtensions.SynchronizeSubfoldersAsync(IFolderSynchronizer synchronizer, Folder folder, SynchronizationPriority priority, CancellationToken cancellationToken)
at MailClient.Protocols.Exchange.ExchangeAccount.SynchronizeIntAsync(Boolean forced)
at MailClient.Protocols.Common.SynchronizableMailAccount.<>c__DisplayClass6_0.<b__0>d.MoveNext()
GUIStatus_Exception_Reported = True