RadzenDropDown: when using multi-select, collections bound to value are set to null on clear

[pianomanjh]

Describe the bug
When using RadzenDropDown to make multiple selections bound to a collection, with AllowClear set to true, a user can click to clear all choices from the collection. This results in the bound collection property being set to null, instead of clearing the collection entries. I understand this may be by design, but, especially when using nullable annotations in a codebase, results in easy-to-miss null reference exceptions.

To Reproduce
Steps to reproduce the behavior:

public class Foo
{
    public ICollection<string> Settings { get; set; } = new List<string>();
}

var foo = new Foo() { Settings = ["Two"] };
var values = new string[] { "One", "Two", "Three" };

<RadzenDropDown Multiple="true" AllowClear="true" @bind-Value="@foo" Data="@values" />

After clicking the X in the control to clear the selections, foo.Settings is null instead of an empty collection.

Expected behavior
If the property bound to value started as a non-null collection instance, I would expect that collection to remain, but be empty.

I understand this may be breaking behavior, so, as a potential mitigation, if the property bound to value started as null, we could have that property be set to null on clear...

Additional context
If this is something the team is ok changing, let me know and I'm happy to post a PR.