When in playmode objects in the heirarchy are not selectable.

Steps to reproduce
- Open project in 2019.3.0a12
- Open the Overworld scene
- Enter playmode
- Try and select any object in the heirarchy
Notice issue >> objects are not selectable.

Seems to only appeart in Ubuntu (18.04.3 LTS)

Note:
I'm seeing an error appear only once when entering playmode, to do with the UGUI.
ArgumentException: SceneManager.SetActiveScene failed; the internal DontDestroyOnLoad scene cannot be set active.
UnityEngine.SceneManagement.SceneManager.SetActiveScene (UnityEngine.SceneManagement.Scene scene) <0x416fd330 + 0x00043> in <cca6e7291a1642cba0657325c21f8848>:0
UnityEditor.SceneHierarchy.TreeViewItemDoubleClicked (System.Int32 instanceID) (at /home/builduser/buildslave/unity/build/Editor/Mono/SceneHierarchy.cs:629)
UnityEditor.IMGUI.Controls.TreeViewController.HandleUnusedMouseEventsForItem (UnityEngine.Rect rect, UnityEditor.IMGUI.Controls.TreeViewItem item, System.Int32 row) (at /home/builduser/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewController.cs:328)
UnityEditor.IMGUI.Controls.TreeViewController.DoItemGUI (UnityEditor.IMGUI.Controls.TreeViewItem item, System.Int32 row, System.Single rowWidth, System.Boolean hasFocus) (at /home/builduser/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewController.cs:508)
UnityEditor.IMGUI.Controls.TreeViewController.IterateVisibleItems (System.Int32 firstRow, System.Int32 numVisibleRows, System.Single rowWidth, System.Boolean hasFocus) (at /home/builduser/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewController.cs:692)
UnityEditor.IMGUI.Controls.TreeViewController.OnGUI (UnityEngine.Rect rect, System.Int32 keyboardControlID) (at /home/builduser/buildslave/unity/build/Editor/Mono/GUI/TreeView/TreeViewController.cs:595)
UnityEditor.SceneHierarchy.DoTreeView (System.Single searchPathHeight) (at /home/builduser/buildslave/unity/build/Editor/Mono/SceneHierarchy.cs:794)
UnityEditor.SceneHierarchy.OnGUI (UnityEngine.Rect rect) (at /home/builduser/buildslave/unity/build/Editor/Mono/SceneHierarchy.cs:592)
UnityEditor.SceneHierarchyWindow.DoSceneHierarchy () (at /home/builduser/buildslave/unity/build/Editor/Mono/SceneHierarchyWindow.cs:150)
UnityEditor.SceneHierarchyWindow.OnGUI () (at /home/builduser/buildslave/unity/build/Editor/Mono/SceneHierarchyWindow.cs:133)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <ad04dee02e7e4a85a1299c7ee81c79f6>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <ad04dee02e7e4a85a1299c7ee81c79f6>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <ad04dee02e7e4a85a1299c7ee81c79f6>:0)
UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at /home/builduser/buildslave/unity/build/Editor/Mono/HostView.cs:369)
UnityEditor.HostView.Invoke (System.String methodName) (at /home/builduser/buildslave/unity/build/Editor/Mono/HostView.cs:363)
UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition, UnityEngine.Rect viewRect) (at /home/builduser/buildslave/unity/build/Editor/Mono/HostView.cs:339)
UnityEditor.DockArea.DrawView (UnityEngine.Rect viewRect, UnityEngine.Rect dockAreaRect) (at /home/builduser/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:366)
UnityEditor.DockArea.OldOnGUI () (at /home/builduser/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:356)
UnityEngine.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 parentTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout, UnityEngine.Rect layoutSize, System.Boolean eventIsPropagatedFromNonFocusableVisualElement) (at /home/builduser/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:291)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Boolean eventIsPropagatedFromNonFocusableVisualElement) (at /home/builduser/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:501)
UnityEngine.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, System.Boolean eventIsPropagatedFromNonFocusableVisualElement) (at /home/builduser/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:484)
UnityEngine.UIElements.IMGUIContainer.SendEventToIMGUI (UnityEngine.UIElements.EventBase evt) (at /home/builduser/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:475)
UnityEngine.UIElements.IMGUIContainer.HandleEvent (UnityEngine.UIElements.EventBase evt) (at /home/builduser/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:447)
UnityEngine.UIElements.EventDispatchUtilities.PropagateEvent (UnityEngine.UIElements.EventBase evt) (at /home/builduser/buildslave/unity/build/Modules/UIElements/Events/IEventDispatchingStrategy.cs:81)
UnityEngine.UIElements.MouseEventDispatchingStrategy.DispatchEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at /home/builduser/buildslave/unity/build/Modules/UIElements/Events/MouseEventDispatchingStrategy.cs:53)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at /home/builduser/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:277)
UnityEngine.UIElements.EventDispatcher.ProcessEventQueue () (at /home/builduser/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:238)
UnityEngine.UIElements.EventDispatcher.OpenGate () (at /home/builduser/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:203)
UnityEngine.UIElements.EventDispatcherGate.Dispose () (at /home/builduser/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:44)
UnityEngine.UIElements.EventDispatcher.ProcessEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel) (at /home/builduser/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:310)
UnityEngine.UIElements.EventDispatcher.Dispatch (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.IPanel panel, UnityEngine.UIElements.DispatchMode dispatchMode) (at /home/builduser/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:159)
UnityEngine.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.UIElements.EventBase e, UnityEngine.UIElements.DispatchMode dispatchMode) (at /home/builduser/buildslave/unity/build/Modules/UIElements/Panel.cs:245)
UnityEngine.UIElements.UIElementsUtility.DoDispatch (UnityEngine.UIElements.BaseVisualElementPanel panel) (at /home/builduser/buildslave/unity/build/Modules/UIElements/UIElementsUtility.bindings.cs:359)
UnityEngine.UIElements.UIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at /home/builduser/buildslave/unity/build/Modules/UIElements/UIElementsUtility.bindings.cs:154)
UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at /home/builduser/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:179)