I'd like to create a small niche on the side of a wall opening. I created it using the niche command like in the plan below.


But the 3D shows a fake line with zero thickness but visible. 


Is there any trick to do it? I already tried without success to: 

- enlarge a bit the niche beyond wall opening: still visible

- create first the niche: cannot create the wall opening

- create a niche larger than the walll opening: cannot insert it

- edit the room with interion modeling (1.0 or 2.0): cannot edit the wall inside itself but extrude inside the room