How do I stop the centre of this arch extrude from filling in?

Thanks, Brent


I am using the 1D extrude along path script. Is there a better way? Thanks

I deleted the centre geometry by selecting near the centre and choosing select more until it would select no more and hit delete. I was then left with a perfect extrude. I found a better way of doing this at the blender stack exchange and my results are at the following link. Thanks