[horde] remove portal blocks

[Rick Emery]

Quoting Eric Rostetter <eric.rostetter at physics.utexas.edu>:

> Yes, I ran into the 'deleting a block leaves an empty block in its place'
> and I simply used the movement arrows to move it down to the bottom where it
> is
> harmless.
>
> --
> Eric Rostetter
> The Department of Physics
> The University of Texas at Austin
>
> Why get even? Get odd!

I'll have to remember that in case I need it in the future.

Thanks,
Rick