NullReferenceException when clicking on "Analyze"

I am using Unity 2018.3 beta 6, this happens when i click on "Analyze" from the "Addressable assets" window toolbar:

Code (CSharp):

1. NullReferenceException: Object reference not set to an instance of an object
2. UnityEditor.AddressableAssets.AssetSettingsAnalyzeTreeView.BuildRoot () (at Library/PackageCache/com.unity.addressables@0.4.6-preview/Editor/GUI/AssetSettingsAnalyze.cs:113)
3. UnityEditor.IMGUI.Controls.TreeView+TreeViewControlDataSource.FetchData () (at C:/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewControl/TreeViewControlDataSource.cs:53)
4. UnityEditor.IMGUI.Controls.TreeViewDataSource.ReloadData () (at C:/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewDataSource.cs:53)
5. UnityEditor.IMGUI.Controls.TreeView+TreeViewControlDataSource.ReloadData () (at C:/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewControl/TreeViewControlDataSource.cs:25)
6. UnityEditor.IMGUI.Controls.TreeViewController.ReloadData () (at C:/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewController.cs:289)
7. UnityEditor.IMGUI.Controls.TreeView.Reload () (at C:/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewControl/TreeViewControl.cs:105)
8. UnityEditor.AddressableAssets.AssetSettingsAnalyze.OnGUI (UnityEngine.Rect pos, UnityEditor.AddressableAssets.AddressableAssetSettings settings) (at Library/PackageCache/com.unity.addressables@0.4.6-preview/Editor/GUI/AssetSettingsAnalyze.cs:47)
9. UnityEditor.AddressableAssets.AddressableAssetsSettingsGroupEditor.OnGUI (UnityEngine.Rect pos) (at Library/PackageCache/com.unity.addressables@0.4.6-preview/Editor/GUI/AddressableAssetsSettingsGroupEditor.cs:372)
10. UnityEditor.AddressableAssets.AddressableAssetsWindow.OnGUI () (at Library/PackageCache/com.unity.addressables@0.4.6-preview/Editor/GUI/AddressableAssetsWindow.cs:131)
11. System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <ac823e2bb42b41bda67924a45a0173c3>:0)
12. Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
13. System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <ac823e2bb42b41bda67924a45a0173c3>:0)
14. System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <ac823e2bb42b41bda67924a45a0173c3>:0)
15. UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:342)
16. UnityEditor.HostView.Invoke (System.String methodName) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:336)
17. UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition, UnityEngine.Rect viewRect) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:310)
18. UnityEditor.DockArea.DrawView (UnityEngine.Rect viewRect, UnityEngine.Rect dockAreaRect, System.Boolean customBorder, System.Boolean floatingWindow, System.Boolean isBottomTab) (at C:/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:363)
19. UnityEditor.DockArea.OldOnGUI () (at C:/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:322)
20. UnityEngine.Experimental.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout) (at C:/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:266)
21. UnityEngine.Experimental.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect) (at C:/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:438)
22. UnityEngine.Experimental.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e) (at C:/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:421)
23. UnityEngine.Experimental.UIElements.IMGUIContainer.HandleEvent (UnityEngine.Experimental.UIElements.EventBase evt) (at C:/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:401)
24. UnityEngine.Experimental.UIElements.EventDispatcher.ProcessEvent (UnityEngine.Experimental.UIElements.EventBase evt, UnityEngine.Experimental.UIElements.IPanel panel) (at C:/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:511)
25. UnityEngine.Experimental.UIElements.EventDispatcher.Dispatch (UnityEngine.Experimental.UIElements.EventBase evt, UnityEngine.Experimental.UIElements.IPanel panel, UnityEngine.Experimental.UIElements.DispatchMode dispatchMode) (at C:/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:307)
26. UnityEngine.Experimental.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.Experimental.UIElements.EventBase e, UnityEngine.Experimental.UIElements.DispatchMode dispatchMode) (at C:/buildslave/unity/build/Modules/UIElements/Panel.cs:176)
27. UnityEngine.Experimental.UIElements.UIElementsUtility.DoDispatch (UnityEngine.Experimental.UIElements.BaseVisualElementPanel panel) (at C:/buildslave/unity/build/Modules/UIElements/UIElementsUtility.cs:245)
28. UnityEngine.Experimental.UIElements.UIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at C:/buildslave/unity/build/Modules/UIElements/UIElementsUtility.cs:68)
29. UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at C:/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:179)