nitrogen tissue saturation toggle is broken

[Salvo Tomaselli]

> But they are linked, so if you don’t display the ceiling the other two have no effect.

Thank you. So I think that they should get disabled if the 1st button
is not set.

Also, my initial situation was that somehow the ceiling was not
displayed but the saturation (2nd buttonI) was. But after I touched
them, I could no longer reach that state. I think this is a bug, but I
don't know how it got in that state originally.