[Windows][Material][ToggleButton] Using MaterialIconToggleButtonStyle without setting AlternateContent causes a crash when toggling

[kazo0]

WINDOWS ONLY

When using a ToggleButton with the style: MaterialIconToggleButtonStyle, if I do not set the um:ControlExtensions.AlternateContent, the app will crash when I attempt to toggle the button by clicking on it.

So the following XAML causes a crash:

<ToggleButton Style="{StaticResource MaterialIconToggleButtonStyle}">
	<ToggleButton.Content>
		<SymbolIcon Symbol="Accept" />
	</ToggleButton.Content>
</ToggleButton>

While the following XAML works fine:

<ToggleButton Style="{StaticResource MaterialIconToggleButtonStyle}">
	<ToggleButton.Content>
		<SymbolIcon Symbol="Accept" />
	</ToggleButton.Content>
	<um:ControlExtensions.AlternateContent>
		<SymbolIcon Symbol="Delete" />
	</um:ControlExtensions.AlternateContent>
</ToggleButton>

Repro app

UnoApp5.zip

[agneszitte]

Re-Open for Backport PR

[trydalch]

I'm running into a related issue here.

I don't need to use the alternate content, and would like the Content to not be hidden when I toggle the button. Is there a way to only hide the Content if AlternateContent is set?

This seems more in line with the WinUI ToggleButton behavior.