MissingReferenceException is thrown while saving a tile palette

Steps to reproduce:
1. Create a new unity project.
2. Window >> Tile Palette.
3. Create new palette from Tile Palette tab
4. Give name and path to save palette.

Observe that Missing Reference Exception is thrown on console.

Reproducible With:
Unity 2018.2.0a7, 2018.2.0a3, 2018.2.0a2, 2018.2.0a1

Works fine with:
Unity 2018.1.0b13, 2017.3.0f3

Environment:
Only on Mac 10.13, Mac10.12

Error Details :
MissingReferenceException: The object of type 'ContainerWindow' has been destroyed but you are still trying to access it.
Your script should either check if it is null or you should not destroy the object.
UnityEditor.ContainerWindow.Close () (at /Users/builduser/buildslave/unity/build/Editor/Mono/ContainerWindow.cs:157)
UnityEditor.EditorWindow.Close () (at /Users/builduser/buildslave/unity/build/Editor/Mono/EditorWindow.cs:823)
UnityEditor.GridPaletteAddPopup.OnGUI () (at /Users/builduser/buildslave/unity/build/Modules/TilemapEditor/Editor/Managed/Grid/GridPaletteAddPopup.cs:113)
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:222)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MonoMethod.cs:232)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at /Users/builduser/buildslave/mono/build/mcs/class/corlib/System.Reflection/MethodBase.cs:115)
UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at /Users/builduser/buildslave/unity/build/Editor/Mono/HostView.cs:295)
UnityEditor.HostView.Invoke (System.String methodName) (at /Users/builduser/buildslave/unity/build/Editor/Mono/HostView.cs:288)
UnityEditor.HostView.OldOnGUI () (at /Users/builduser/buildslave/unity/build/Editor/Mono/HostView.cs:104)
UnityEngine.Experimental.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt) (at /Users/builduser/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:217)