Rhino 8 UI issues: panel background styling

[Gijs (Gijs de Zwart)]

Continuing the discussion from V8 UI styling & customization thread:

@eobet

When a named panel background has nothing in it, it’s the content background color (which is fine), but when it’s populated it suddenly has an entirely different non styled color (and both cases has a 1 pixel outline which other panels lack).

[Gijs (Gijs de Zwart)]

RH-81664 Panel styling consistency