Error when switching from subtitling to other project

I get an "Object reference not set to ..." error if I do the following:

  1. Open a vtt file with subtitling preview for translation.
  2. Close the file.
  3. Switch to another project.
  4. Open a (non-subtitling) file for translation. This is when the error pops up.

I tried a few things like pinning/unpinning the subtitling preview window (It's on a second screen, outside the main Studio window), closing it before closing the vtt file, but it does not solve the problem. Restarting Studio clears it.

Daniel

Here's the stack trace:

sdlerror-2019814-8h22m12s.sdlerror.xml
<SDLErrorDetails time="14-Aug-19 08:22:18">
  <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>StudioSubtitling</Source>
    <HResult>-2147467261</HResult>
    <StackTrace><![CDATA[   at StudioSubtitling.Services.TimelineMarkerService.GetTimelineMarkers(IEnumerable`1 segmentPairs, ProjectFile activeFile, DocumentFileInfo mergedFileInfo)
   at StudioSubtitling.ViewModel.MediaElementViewModel.UpdateTimelineMarkers(DocumentFileInfo mergedFileInfo)
   at StudioSubtitling.ViewModel.MediaElementViewModel.SetActiveFile(ProjectFile projectFile)
   at StudioSubtitling.ViewModel.MediaElementViewModel.SetActiveDocument(Document document)
   at StudioSubtitling.ViewModel.MediaElementViewModel.EditorController_ActiveDocumentChanged(Object sender, DocumentEventArgs e)
   at System.EventHandler`1.Invoke(Object sender, TEventArgs e)
   at Sdl.Desktop.Platform.Extensions.EventsExtensions.Raise[T](EventHandler`1 e, Object sender, T eventArgs)
   at Sdl.TranslationStudioAutomation.IntegrationApi.EditorController.OnActiveDocumentChanged(IDocument document)
   at Sdl.TranslationStudio.Api.Editor.DocumentEventHandler.Invoke(IDocument document)
   at Sdl.TranslationStudio.Editor.EditorService.set_ActiveDocument(IDocument value)
   at Sdl.TranslationStudio.Editor.EditorView.OnActiveViewPartChanged(IViewPartReference viewPartReference)
   at Sdl.Desktop.Platform.AbstractViewWithParts.Control_ActiveViewPartChanged(IViewWithParts view, IViewPartReference viewPartReference)
   at Sdl.Desktop.Platform.WinForms.DockingViewContentControl.OnActiveViewPartChanged(IViewPartReference viewPartReference)
   at Sdl.Desktop.Platform.WinForms.DockingViewContentControl.InternalActivateViewPart(IViewPartReference viewPartToActivate)
   at Sdl.Desktop.Platform.WinForms.DockingViewContentControl._tabControl_SelectedTabChanged(Object sender, SelectedTabChangedEventArgs e)
   at Infragistics.Win.UltraWinTabControl.UltraTabControlBase.OnSelectedTabChanged(SelectedTabChangedEventArgs e)
   at Infragistics.Win.UltraWinTabControl.UltraTabControlBase.RaiseEvent(UltraTabControlEventId id, EventArgs e)
   at Infragistics.Win.UltraWinTabControl.UltraTabControlBase.OnManagerSelectedTabItemChanged(Object sender, SelectedTabItemChangedEventArgs e)
   at Infragistics.Win.UltraWinTabs.TabManager.set_SelectedTabItem(ITabItem value)
   at Infragistics.Win.UltraWinTabControl.UltraTabControlBase.SetSelectedTab(UltraTab tab)
   at Infragistics.Win.UltraWinTabControl.UltraTabControlBase.set_SelectedTab(UltraTab value)
   at Sdl.Desktop.Platform.WinForms.DockingViewContentControl.AddViewPartTab(IViewPartReference viewPartReference)
   at Sdl.Desktop.Platform.WinForms.DockingViewContentControl.AddViewPart(IViewPartReference viewPartReference)
   at Sdl.Desktop.Platform.WinForms.DockingViewContentControl.NotifyViewPartAdded(IViewPartReference viewPartReference)
   at Sdl.Desktop.Platform.AbstractViewWithParts.AddViewPart(IViewPartReference viewPartReference)
   at Sdl.Desktop.Platform.AbstractDockingView.AddViewPart(IViewPartReference viewPartReference)
   at Sdl.TranslationStudio.Editor.Shared.InternalEditorContext.AddDocumentViewPart(IDocumentViewPart documentViewPart)
   at Sdl.TranslationStudio.Api.Editor.AbstractInternalDocument.AfterLoad(IJob job)]]></StackTrace>
  </Exception>
  <Environment>
    <ProductName>SDL Trados Studio</ProductName>
    <ProductVersion>15.0.0.0</ProductVersion>
    <EntryAssemblyFileVersion>15.2.0.1041</EntryAssemblyFileVersion>
    <OperatingSystem>Microsoft Windows 10 Enterprise</OperatingSystem>
    <ServicePack>NULL</ServicePack>
    <OperatingSystemLanguage>1033</OperatingSystemLanguage>
    <CodePage>1252</CodePage>
    <LoggedOnUser>danielhug</LoggedOnUser>
    <DotNetFrameWork>4.0.30319.42000</DotNetFrameWork>
    <ComputerName>ABCDE</ComputerName>
    <ConnectedToNetwork>True</ConnectedToNetwork>
    <PhysicalMemory>12581868 MB</PhysicalMemory>
  </Environment>
</SDLErrorDetails>