NavigationView: PaneFooter containing NavigationViewItem crashes app when navigating focus via TAB to Settings item (Regression)

[Felix-Dev]

Describe the bug
When putting a NavigationViewItem inside the NavigationView.PaneFooter area as the last item and then moving focus to the NavigationView's in-built Settings item via TAB, the app crashes:

<muxc:NavigationView>
    <muxc:NavigationView.MenuItems>
        <muxc:NavigationViewItem Icon="Home" Content="Home"/>
    </muxc:NavigationView.MenuItems>

    <muxc:NavigationView.PaneFooter>
        <muxc:NavigationViewItem>
            <muxc:NavigationViewItem.Content>
                <StackPanel Orientation="Horizontal">
                    <PersonPicture Width="20" Height="20" />
                    <TextBlock Text="Account" Margin="10,0,0,0" />
                </StackPanel>
            </muxc:NavigationViewItem.Content>
        </muxc:NavigationViewItem>
    </muxc:NavigationView.PaneFooter>
</muxc:NavigationView>

Note that for the crash to happen, an existing NavigationViewItem needs to be selected when moving focus. This is a regression which first occurs in WinUI 2.5.0-prerelease.200812001 and is probably caused by PR #1997.

Expected behavior
App should not crash and focus should move to Settings item.

NuGet package version:

• Microsoft.UI.Xaml 2.5.0-prerelease.200812001
• Microsoft.UI.Xaml v2.5.0-prerelease.200923002

Additional context
I would like to take a look at this. I might have to write an interaction test though and I'm currently blocked on PR #3359. If that PR will take a while to be merged, and a fix for this issue needs to get out real fast (depending on WinUI's 2.5 release plan) then someone else without my interaction test issues is probably a better choice to work on this. @StephenLPeters to comment (seems like unrelated test pipeline issue(s) need to be resolved first for that PR to be merged).

[ranjeshj]

@Felix-Dev Thanks for filing the issue. Please go ahead with your investigation. Thanks!

[ranjeshj]

@YuliKl as FYI