Null reference exception in the MultiSelectorHelper

[vicitacal]

Describe the bug

I use MultiSelectorHelper.SelectedItems in the DataTemplate and get a NullReferenceException every time this DataTemplate is changed to another one.

Steps to reproduce

Run demo and just change selected value in the combo box.

https://github.com/vicitacal/MahAppsBugDemo

Expected behavior

Template change successfully.

Actual behavior

Exception crush application.

Environment

MahApps.Metro version: v2.4.10
Windows build number: Win10 21H2
Visual Studio: 2022 17.9.2
Target Framework: .Net Core 6 (6.0.133)