*Steps to reproduce:*
# Open a visual novel graph
# Create a bunch of variables (until it exceeds the height of the overlay)
# Scroll down to the bottom
# Create a bunch more variables

*Actual results:* Occasionally, an error is thrown

*Expected results:* No error is thrown

*Tested on (OS):* MacOS

{*}Stack trace{*}:
{code:java}
Observer Unity.GraphToolkit.Editor.ModelViewUpdater does not specify that it modifies Unity.GraphToolkit.Editor.BlackboardViewStateComponent. Please add the state component to its ModifiedStateComponents.
UnityEngine.Debug:LogError (object)
Unity.GraphToolkit.CSO.StateComponent`1/BaseUpdater`1<Unity.GraphToolkit.Editor.BlackboardViewStateComponent/StateUpdater, Unity.GraphToolkit.Editor.BlackboardViewStateComponent>:Initialize (Unity.GraphToolkit.CSO.IStateComponent) (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/CommandStateObserver/States/StateComponent.cs:87)
Unity.GraphToolkit.CSO.StateComponent`1<Unity.GraphToolkit.Editor.BlackboardViewStateComponent/StateUpdater>:get_UpdateScope () (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/CommandStateObserver/States/StateComponent.cs:214)
Unity.GraphToolkit.Editor.BlackboardView:OnVerticalScroll (UnityEngine.UIElements.ChangeEvent`1<single>) (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/GraphToolkitEditor/UI/Views/Blackboard/BlackboardView.cs:240)
UnityEngine.UIElements.ScrollView:set_scrollOffset (UnityEngine.Vector2)
Unity.GraphToolkit.Editor.Blackboard:UpdateFromModel () (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/GraphToolkitEditor/UI/ModelView/Blackboard/ModelView/Blackboard.cs:495)
Unity.GraphToolkit.Editor.Blackboard:UpdateUIFromModel (Unity.GraphToolkit.Editor.UpdateFromModelVisitor) (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/GraphToolkitEditor/UI/ModelView/Blackboard/ModelView/Blackboard.cs:461)
Unity.GraphToolkit.Editor.BlackboardView:Update () (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/GraphToolkitEditor/UI/Views/Blackboard/BlackboardView.cs:306)
Unity.GraphToolkit.Editor.ModelViewUpdater:Observe () (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/GraphToolkitEditor/UI/Views/ModelViewUpdater.cs:41)
Unity.GraphToolkit.CSO.ObserverManager:NotifyObservers (Unity.GraphToolkit.CSO.IState) (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/CommandStateObserver/ObserverManager.cs:269)
Unity.GraphToolkit.CSO.CsoTool:Update () (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/CommandStateObserver/CsoTool.cs:128)
Unity.GraphToolkit.Editor.GraphTool:Update () (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/GraphToolkitEditor/EditorCommon/CommandStateObserver/GraphTool.cs:290)
Unity.GraphToolkit.Editor.GraphViewEditorWindow:EditorUpdate () (at ./Library/PackageCache/com.unity.graphtoolkit@76e4289d7ea6/GraphToolkitEditor/UI/Windows/GraphViewEditorWindow.cs:1269)
UnityEditor.EditorApplication:Internal_CallUpdateFunctions () (at /Users/bokken/build/output/unity/unity/Editor/Mono/EditorApplication.cs:384)
{code}