Please help.

Suddenly the file in translation is blocked.

Below are the details of the erros message.

 <SDLErrorDetails time="6/20/2017 11:55:16 AM">
<ErrorMessage>Object reference not set to an instance of an object.</ErrorMessage>
<Exception>
<Type>System.NullReferenceException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>
<HelpLink />
<Source>Sdl.TranslationStudio.Editor</Source>
<HResult>-2147467261</HResult>
<StackTrace><![CDATA[ at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocument.GetRevisions()
at Sdl.TranslationStudio.Editor.TranslationEditor.TranslatableDocument.Close()
at Sdl.TranslationStudio.Editor.EditorService.<CloseAllDocuments>b__4e(IDocument t)
at System.Linq.Enumerable.All[TSource](IEnumerable`1 source, Func`2 predicate)
at Sdl.TranslationStudio.Editor.EditorService.CloseAllDocuments()
at Sdl.TranslationStudio.Editor.EditorService.Window_Closing(IStudioWindow window, CancelEventArgs e)
at Sdl.Desktop.Platform.StudioWindowCancelEventHandler.Invoke(IStudioWindow window, CancelEventArgs cancel)
at Sdl.Desktop.Platform.Implementation.StudioWindow.OnClosing()
at Sdl.Desktop.Platform.Implementation.StudioWindow._form_Closing(Object sender, CancelEventArgs e)
at System.Windows.Forms.Form.OnClosing(CancelEventArgs e)
at System.Windows.Forms.Form.WmClose(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at Sdl.Desktop.Platform.WinForms.StudioWindowForm.WndProc(Message& message)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)]]></StackTrace>
</Exception>
<Environment>
<ProductName>SDL Trados Studio</ProductName>
<ProductVersion>14.0.0.0</ProductVersion>
<EntryAssemblyFileVersion>14.0.5889.5</EntryAssemblyFileVersion>
<OperatingSystem>Microsoft Windows 10 Pro</OperatingSystem>
<ServicePack>NULL</ServicePack>
<OperatingSystemLanguage>1033</OperatingSystemLanguage>
<CodePage>1250</CodePage>
<LoggedOnUser>MILOSJOVANOVIC\Milos Jovanovic</LoggedOnUser>
<DotNetFrameWork>4.0.30319.42000</DotNetFrameWork>
<ComputerName>MILOSJOVANOVIC</ComputerName>
<ConnectedToNetwork>True</ConnectedToNetwork>
<PhysicalMemory>4127400 MB</PhysicalMemory>
</Environment>
</SDLErrorDetails>

Thank you in advance,

Miloš