"Object reference not set to an instance of an object" when importing arguments within Invoke Workflow activity on latest 2019.5 beta

I’ve just updated and I’ve found a reproducible bug

  1. invoke a workflow that has arguments

  2. import arguments

  3. fill in the arguments (only one is enough) and click ok

     Error: System.NullReferenceException: Object reference not set to an instance of an object.
        at UiPath.Studio.Plugin.Workflow.WorkflowHandling.DocumentBreakpointsService.ModelService_ModelChanged(Object sender, ModelChangedEventArgs ev)
        at System.EventHandler`1.Invoke(Object sender, TEventArgs e)
        at System.Activities.Presentation.Model.ModelServiceImpl.OnModelItemsRemoved(IEnumerable`1 modelItems)
        at System.Activities.Presentation.Model.ModelTreeManager.CollectionClear(ModelItemCollectionImpl modelItemCollectionImpl)
        at System.Activities.Presentation.Model.ModelItemCollectionImpl.Clear()
        at System.Activities.Presentation.DynamicArgumentDesigner.WrapperCollectionToModelItem(ObservableCollection`1 wrappers, ModelItem data, Boolean isDictionary, Type underlyingArgumentType)
        at System.Activities.Presentation.DynamicArgumentDialog.OnWorkflowElementDialogClosed(Nullable`1 dialogResult)
        at System.Activities.Presentation.WorkflowElementDialog.<Show>b__48_0(Object s, EventArgs e)
        at System.EventHandler.Invoke(Object sender, EventArgs e)
        at System.Windows.Window.OnClosed(EventArgs e)
        at System.Windows.Window.WmDestroy()
        at System.Windows.Window.WindowFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
        at System.Windows.Interop.HwndSource.PublicHooksFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
        at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
        at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
        at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
        at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler), HResult -2147467261

Hi @c.ciprian

(Un)fortunately, this exact scenario seems to be working for me with no issues on the latest beta 2019.5.0-beta.10.

Have you tried on a blank project? Also, does it happen exactly after clicking the Ok or after running the project?

Hi @loginerror,

I have tried on beta 8, but now on beta 10 the scenario is reproducible.
I have tried on a blank project and it happens right after clicking the Ok. I can do additional debugging if you need (just give the methodology).

L.E. : beta 19 same issue (tested on 2 separate Win 10)

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Third test on a new VM with the same results

@c.ciprian We are aware of this problem and is work in progress on our side. We know how to replicate the issue.

Thanks for your help


Beta 24 works ok

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