Enable in-app Toolbar in XAML Hot Reload crashes in App SDK 1.5

[JochemPalmsens]

Describe the bug

This is a kind-of successor to #8806 I managed to get a situation where the application crashes when the XAML Hot Reload in-app toolbar is enabled, but now in WinAppSDK 1.5.240627000

Steps to reproduce the bug

I haven't pin-pointed it precisely, but it seems to happen when a new window (in our case containing a webview 2 element) is quickly opened and closed. (We use it for OAuth0 logout)

Expected behavior

Of course we expect the application not to crash. We have no issues when we disable the in-app toolbar

Screenshots

Exception:

Call stack:

NuGet package version

WinUI 3 - Windows App SDK 1.5.5: 1.5.240627000

Windows version

Windows 11 (22H2): Build 22621

Additional context

Visual Studio Professional 17.10.5

I would be glad to help debug this, but I don't know where to begin. The screenshot shows a null-reference exception

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Closed similar issues:

• Enable in-app Toolbar in XAML Hot Reload crashes in App SDK 1.4 (#8806), similarity score: 0.85

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[JochemPalmsens]

I managed to get some disassebly info:

[wbokkers]

I see the same issue in App SDK 1.6 when closing a (child) Window.