The bug

Trying to place a structure void block by right clicking an existing structure void block does not work.

This makes placing a large open area of structure void blocks difficult as you need to place solid blocks first, place the void blocks against them, then remove the solid blocks.

How to reproduce

1. For easy viewing of void blocks, place a save structure block with a decent sized volume and check the "show invisible blocks" option.
2. Place a structure void block within the bounding box.
3. Try to place another structure void block on top of the placed one.