[ListBaseComponent] Fix for default selection options (#4135)

Author: Tyme-Bleyaert

src/Core/Components/List/FluentCombobox.razor.cs

@@ -167,7 +167,7 @@ protected override async Task ChangeHandlerAsync(ChangeEventArgs e)
     {
         if (SelectedOption != null)
         {
-            return OptionText.Invoke(SelectedOption) ?? OptionValue.Invoke(SelectedOption) ?? SelectedOption.ToString();
+            return OptionText.Invoke(SelectedOption) ?? OptionValue?.Invoke(SelectedOption) ?? SelectedOption.ToString();
         }
         else
         {

src/Core/Components/List/ListComponentBase.razor.cs

@@ -115,7 +115,7 @@ protected string? InternalValue
     /// Only for <see cref="FluentListbox{TOption}"/> and <see cref="FluentSelect{TOption}"/> components.
     /// </summary>
     [Parameter]
-    public virtual Func<TOption, string?> OptionValue { get; set; }
+    public virtual Func<TOption, string?>? OptionValue { get; set; }
 
     /// <summary>
     /// Gets or sets the function used to determine if an option is disabled.
@@ -220,7 +220,6 @@ protected ListComponentBase()
         Id = Identifier.NewId();
 
         OptionText = (item) => item?.ToString() ?? null;
-        OptionValue = (item) => OptionText.Invoke(item) ?? item?.ToString() ?? null;
 
         _renderOptions = RenderOptions;
     }