PropertyGrid - text is invisible in all the "Light" themes

[MikePelton]

All text in all the "Light." themes for a PropertyGrid is coloured a very pale blue and hence unreadable. Weirdly the Avalonia DevTools Diagnostic reports the foreground colour as Black, so it looks like some inner chunk of the textbox template is somehow finding that pale colour. This effect shows up in the demo application, and can also be seen if you put a preview control textbox into (for example) Light.Blue.axaml.

  <Design.PreviewWith>
        <Border Padding="20">
            <TextBox>Banana</TextBox>
        </Border>
    </Design.PreviewWith>

Putting a TextBlock in instead gets the expected black text.