Foundation issue between buildings

I have a cell block that I want to connect to a newer cell block. I created the foundation, then wanted to create a secure inside tunnel (with regular foundation) between the two for ease of workers, guards, etc, putting jail doors on both sides. I selected the foundation tool and created a path between, but it complained that an entrance was required, even though both ends have a large jail door.

After the fact, I realized that I didn't make it wide enough because the foundation includes the walls, so I wanted to remove it, but now I can't interact with it at all. I can't demolish what's there, and no workers (even when completely idle) will not work on it. I'm not sure what my options are now. I'd be fine deleting the path between the cell blocks if I can, so I can have another attempt at creating one.

Any suggestions would be appreciated on either how to finish the path with foundation (not just concrete tiles) or delete what's there.