MissingReferenceException is thrown on canceling "Can't add the same component multiple times!" pop-up

Steps to Repro:
1. Open attached or new project
2. Hierarchy > Create a new game object
3. Add component > Rigidbody
4. repeat step 3
5. Click on "Cancel".

Actual result:
Observe that MissingReferenceException is thrown on the console.

Occurring with:
2018.2.0a7, 2018.2.0a5, 2018.2.0a1

Working with:
2018.1.0b13

Environment:
OSX 10.13, OSX 10.12

Stack trace:
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.AdvancedDropdownWindow.CloseWindow () (at /Users/builduser/buildslave/unity/build/Editor/Mono/Inspector/AdvancedDropdown/AdvancedDropdownWindow.cs:222)
UnityEditor.AdvancedDropdownWindow.HandleKeyboard () (at /Users/builduser/buildslave/unity/build/Editor/Mono/Inspector/AdvancedDropdown/AdvancedDropdownWindow.cs:189)
UnityEditor.AdvancedDropdownWindow.OnGUI () (at /Users/builduser/buildslave/unity/build/Editor/Mono/Inspector/AdvancedDropdown/AdvancedDropdownWindow.cs:94)
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)