Unable to make a dimension of just void

I need to make a dimension completely out of void, and ever forum on here about that says to just to just set the main filler and fluid blocks as air, so nothing spawns in. For some reason though, when I try this I just get an error claiming I didn't select anything and makes it so I can't save the element. Its the same for making a biome with the filler block as air. Does anyone know a fix to this yet or a workaround to get a void dimension? Thank you! (I made a reply about this on one of the original forums, but I think that got buried cause it was already "solved", so I'm just going to make a forum post)