[Bug] App crashes while updating SelectorView AllowMultiple property

[zohaibhanif]

Description

I am using SelectorView and Switch control on a page. I am setting up AllowMultiple property of the SelectorView with the Switch toggle. When i run the application with AllowMutiple = false, SelectorView works perfectly fine and only one item can be selected in it. When i toggle the Switch to turn on multiple selection, SelectorView works perfectly fine and multiple items can be selected. When i toggle the Switch back to turn off multiple selection, Application crashes on both iOS and Android.

Steps to reproduce

1. Add a page having Switch and SelectorView controls
2. Added ItemList and MultiSelectEnabled properties to the page view model.
3. Bind ItemList and MultiSelectEnabled to ItemsSource and AllowMultiple of SelectorView control respectively.
4. Bind MultiSelectEnabled to IsToggled of Switch control.
5. Run the application, toggle the Switch to turn on multiple selection and then toggle it again to turn off multiple selection.

Expected Behavior

It should turn off multiple selection and should clear up the items from SelectedItems property.

Actual Behavior

Application crashes on both iOS and Android.

Basic Information

• Version with issue: AP.MobileToolkit - 3.0.0-ci
• Xamarin.Forms version: 4.2.0.815419
• IDE: Visual Studio 2019 Professional - Version 16.3.5

Reproduction Link

Project: ToolkitDemo
Branch: issue/75/Demo-User-Controls