Package Manager window does not open from UDP section in the service window.
ArgumentNullException error is thrown on clicking on the Package Manager tab in Unity Distribution Portal

Steps to repro:
1. Open the attached Project.
2. Windows > General > Services.
3. Unity Distribution Portal > Click on Package Manager tab.

Actual Result:
ArgumentNullException error is thrown in the console window.

Expected Result:
No Errors in the console.

Reproducible in:
2020.1.0a18, 2020.1.0a17.

Note: Package manager tab is introduced in UDP section in Service window in 2020.1.0a17.

Environment:
Occurs only on Windows.

Stack trace:
ArgumentNullException: Value cannot be null.
Parameter name: key
System.Collections.Generic.Dictionary`2[TKey,TValue].FindEntry (TKey key) (at <437ba245d8404784b9fbab9b439ac908>:0)
System.Collections.Generic.Dictionary`2[TKey,TValue].ContainsKey (TKey key) (at <437ba245d8404784b9fbab9b439ac908>:0)
UnityEditor.PackageManager.UI.VisualStateList.Contains (System.String packageUniqueId) (at <50c2886429a849e8b640d0aca52729fc>:0)
UnityEditor.PackageManager.UI.SimplePage.Contains (System.String packageUniqueId) (at <50c2886429a849e8b640d0aca52729fc>:0)
UnityEditor.PackageManager.UI.PageManager+PageManagerInternal.FindTab (System.String versionUniqueIdOrDisplayName) (at <50c2886429a849e8b640d0aca52729fc>:0)
UnityEditor.PackageManager.UI.PackageManagerWindow.SelectPackageAndFilter (System.String packageIdOrDisplayName, System.Nullable`1[T] filterTab, System.Boolean refresh, System.String searchText) (at <50c2886429a849e8b640d0aca52729fc>:0)
UnityEditor.PackageManager.UI.PackageManagerWindow.OpenPackageManager (System.String packageNameOrDisplayName) (at <50c2886429a849e8b640d0aca52729fc>:0)
UnityEditor.Connect.ServicesEditorWindow+<>c__DisplayClass40_0.<SetupPackageInstall>b__0 () (at <50c2886429a849e8b640d0aca52729fc>:0)
UnityEngine.UIElements.Clickable.Invoke (UnityEngine.UIElements.EventBase evt) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.Clickable.ProcessUpEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.Vector2 localPosition, System.Int32 pointerId) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.Clickable.OnMouseUp (UnityEngine.UIElements.MouseUpEvent evt) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.EventCallbackFunctor`1[TEventType].Invoke (UnityEngine.UIElements.EventBase evt) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.EventCallbackRegistry.InvokeCallbacks (UnityEngine.UIElements.EventBase evt) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.CallbackEventHandler.HandleEvent (UnityEngine.UIElements.EventBase evt) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.CallbackEventHandler.HandleEventAtTargetPhase (UnityEngine.UIElements.EventBase evt) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.MouseCaptureDispatchingStrategy.DispatchEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.EventDispatcher.ProcessEventQueue () (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.EventDispatcher.OpenGate () (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.EventDispatcherGate.Dispose () (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.EventDispatcher.Dispatch (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel, UnityEngine.UIElements.DispatchMode dispatchMode) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.UIElements.EventBase e, UnityEngine.UIElements.DispatchMode dispatchMode) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.UIElementsUtility.DoDispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.UIElementsUtility.UnityEngine.UIElements.IUIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr, System.Boolean& eventHandled) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.UIEventRegistration.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.UIElements.UIEventRegistration+<>c.<.cctor>b__1_2 (System.Int32 i, System.IntPtr ptr) (at <7bb8304a61014070b7f28db050747199>:0)
UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at <54db9c4262664587b9517297cb7f0116>:0)