Playing Terran, conquer planet Orlando II from Drengin. It happens on other planets too, but it's there I discovered why I can't place a structure on an empty tile 
The Drengin built the Planetary defense dome on their planet, but there is no graphic appearing. I can see other Drengin buildings allright though.
Saved game:
https://www.dropbox.com/s/g9r99doig63bcpk/missing%20planetary%20defense%20dome%20graphic.GC3Sav?dl=0
I'll file a support ticket later if it ain't already reported.