Transparency Not Shown in Map Preview

Currently, when a map is set to have a hidden background with the base color set to transparent, the map preview does not have the white and grey tiled placeholder like it does while editing the map. It is just black. Considering that many stamps have black in them and there is an entire style of black and white assets, this probably should be changed.

TLDR Change the map preview for transparent maps to have the transparent placeholder background.