fix #1452 значение по умолчанию при добавлении в СписокЗначений

src/ScriptEngine.HostedScript/Library/ValueList/ValueListImpl.cs

@@ -4,10 +4,13 @@ This Source Code Form is subject to the terms of the
 was not distributed with this file, You can obtain one 
 at http://mozilla.org/MPL/2.0/.
 ----------------------------------------------------------*/
+
+using System;
 using ScriptEngine.Machine;
 using ScriptEngine.Machine.Contexts;
 using System.Collections.Generic;
 using System.Linq;
+using ScriptEngine.Machine.Values;
 
 namespace ScriptEngine.HostedScript.Library.ValueList
 {
@@ -76,7 +79,7 @@ public ValueListItem GetValue(IValue index)
  /// <param name="picture">Картинка (необязательный) - Визуальное представление добавляемого значения</param>
  /// <returns>ЭлементСпискаЗначений</returns>
  [ContextMethod("Добавить", "Add")]
- public ValueListItem Add(IValue value, string presentation = null, bool check = false, IValue picture = null)
+ public ValueListItem Add(IValue value = null, string presentation = null, bool check = false, IValue picture = null)
  {
  var newItem = CreateNewListItem(value, presentation, check, picture);
 
@@ -94,7 +97,7 @@ public ValueListItem Add(IValue value, string presentation = null, bool check =
  /// <param name="picture">Картинка (необязательный) - Визуальное представление добавляемого значения</param>
  /// <returns>ЭлементСпискаЗначений</returns>
  [ContextMethod("Вставить", "Insert")]
- public ValueListItem Insert(int index, IValue value, string presentation = null, bool check = false, IValue picture = null)
+ public ValueListItem Insert(int index, IValue value = null, string presentation = null, bool check = false, IValue picture = null)
  {
  var newItem = CreateNewListItem(value, presentation, check, picture);
  _items.Insert(index, newItem);
@@ -105,7 +108,7 @@ public ValueListItem Insert(int index, IValue value, string presentation = null,
  private static ValueListItem CreateNewListItem(IValue value, string presentation, bool check, IValue picture)
  {
  var newItem = new ValueListItem();
- newItem.Value = value;
+ newItem.Value = value ?? UndefinedValue.Instance;
  newItem.Presentation = presentation;
  newItem.Check = check;
  newItem.Picture = picture;
@@ -285,7 +288,7 @@ private int SafeCompare(IValue x, IValue y)
  catch(RuntimeException)
  {
  // Сравнение типов не поддерживается
- return x.AsString().CompareTo(y.AsString());
+ return string.Compare(x?.AsString(), y?.AsString(), StringComparison.Ordinal);
  }
  }