[0.21] Observatory grafic disapear

[Canute0]

When you build an improvment on a tile with an Observatory, the grafic of the observatory disapear.

[Canute0]

on 0.22.0 the grafic still disapear when you improve the tile with an observatory.

[void]

Heya Canute,

Thanks for the reminder, will get to it with the next update that targets several other visual glitches as well!