Enable nullability in ArrayEditor

Author: gpetrou

src/System.Windows.Forms.Design/src/PublicAPI.Shipped.txt

@@ -1,7 +1,7 @@
 #nullable enable
-~override System.ComponentModel.Design.ArrayEditor.CreateCollectionItemType() -> System.Type
-~override System.ComponentModel.Design.ArrayEditor.GetItems(object editValue) -> object[]
-~override System.ComponentModel.Design.ArrayEditor.SetItems(object editValue, object[] value) -> object
+override System.ComponentModel.Design.ArrayEditor.CreateCollectionItemType() -> System.Type!
+override System.ComponentModel.Design.ArrayEditor.GetItems(object? editValue) -> object![]!
+override System.ComponentModel.Design.ArrayEditor.SetItems(object? editValue, object![]? value) -> object?
 ~override System.Windows.Forms.Design.ComponentDocumentDesigner.Initialize(System.ComponentModel.IComponent component) -> void
 ~override System.Windows.Forms.Design.ComponentDocumentDesigner.PreFilterProperties(System.Collections.IDictionary properties) -> void
 ~override System.Windows.Forms.Design.ComponentTray.GetService(System.Type serviceType) -> object
@@ -33,7 +33,7 @@
 ~override System.Windows.Forms.Design.ParentControlDesigner.SnapLines.get -> System.Collections.IList
 ~override System.Windows.Forms.Design.WindowsFormsDesignerOptionService.PopulateOptionCollection(System.ComponentModel.Design.DesignerOptionService.DesignerOptionCollection options) -> void
 ~static System.Windows.Forms.Design.ParentControlDesigner.InvokeCreateTool(System.Windows.Forms.Design.ParentControlDesigner toInvoke, System.Drawing.Design.ToolboxItem tool) -> void
-~System.ComponentModel.Design.ArrayEditor.ArrayEditor(System.Type type) -> void
+System.ComponentModel.Design.ArrayEditor.ArrayEditor(System.Type! type) -> void
 ~System.ComponentModel.Design.DesignerActionMethodItem.DesignerActionMethodItem(System.ComponentModel.Design.DesignerActionList actionList, string memberName, string displayName) -> void
 ~System.ComponentModel.Design.DesignerActionMethodItem.DesignerActionMethodItem(System.ComponentModel.Design.DesignerActionList actionList, string memberName, string displayName, bool includeAsDesignerVerb) -> void
 ~System.ComponentModel.Design.DesignerActionMethodItem.DesignerActionMethodItem(System.ComponentModel.Design.DesignerActionList actionList, string memberName, string displayName, string category) -> void

src/System.Windows.Forms.Design/src/System/ComponentModel/Design/ArrayEditor.cs

@@ -1,8 +1,6 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable disable
-
 namespace System.ComponentModel.Design;
 
 /// <summary>
@@ -22,12 +20,12 @@ public ArrayEditor(Type type) : base(type)
     ///  Gets or sets the data type this collection contains.
     /// </summary>
     protected override Type CreateCollectionItemType()
-        => CollectionType?.GetElementType();
+        => CollectionType?.GetElementType() ?? typeof(object);
 
     /// <summary>
     ///  Gets the items in the array.
     /// </summary>
-    protected override object[] GetItems(object editValue)
+    protected override object[] GetItems(object? editValue)
     {
         if (editValue is Array valueArray)
         {
@@ -42,7 +40,7 @@ protected override object[] GetItems(object editValue)
     /// <summary>
     ///  Sets the items in the array.
     /// </summary>
-    protected override object SetItems(object editValue, object[] value)
+    protected override object? SetItems(object? editValue, object[]? value)
     {
         if (editValue is not null and not Array)
         {