NullReferenceException if a user tries to create tile palette with a blank name or "."

1. Start a new 2D project
2. Window -> Tile Palette
3. In the "Name" field, remove the default and leave it blank
4. Click "Create", click "Select Folder" in the subsequent pop-up

Expected: Warning to user "Cannot create tile palette without a name"
Observed: NullReferenceException

Occurring on: 2017.2.0a4, 2017.2.0a6, 2017.2.0f3, 2017.3.0f3 , 2018.1.0b13, 2018.2.0a7

Asset path error: '' is not valid: Asset path is empty
UnityEngine.GUIUtility:ProcessEvent(Int32, IntPtr)

NullReferenceException
UnityEditor.AssetDatabase.AddObjectToAsset (UnityEngine.Object objectToAdd, UnityEngine.Object assetObject) (at C:/buildslave/unity/build/artifacts/generated/common/editor/AssetDatabaseBindings.gen.cs:201)
UnityEditor.GridPaletteUtility.CreateNewPalette (System.String folderPath, System.String name, CellLayout layout, CellSizing cellSizing, Vector3 cellSize) (at C:/buildslave/unity/build/Modules/TilemapEditor/Editor/Managed/Grid/GridPaletteUtility.cs:65)
UnityEditor.GridPaletteUtility.CreateNewPaletteNamed (System.String name, CellLayout layout, CellSizing cellSizing, Vector3 cellSize) (at C:/buildslave/unity/build/Modules/TilemapEditor/Editor/Managed/Grid/GridPaletteUtility.cs:44)
UnityEditor.GridPaletteAddPopup.OnGUI () (at C:/buildslave/unity/build/Modules/TilemapEditor/Editor/Managed/Grid/GridPaletteAddPopup.cs:77)
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 C:/buildslave/unity/build/Editor/Mono/HostView.cs:283)
UnityEditor.HostView.Invoke (System.String methodName) (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:276)
UnityEditor.HostView.OldOnGUI () (at C:/buildslave/unity/build/Editor/Mono/HostView.cs:105)
UnityEngine.Experimental.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt) (at C:/buildslave/unity/build/Runtime/UIElements/Managed/IMGUIContainer.cs:127)