I changed the default type of return on a field from TEXT to LINK TO USERS PROFILE

Now the form give the error Object reference not set to an instance of an object.

How can I get back into the form to change the field back?  It just gives me the same error when it tries to render.

Once I can get back into the form, I still would like to pull the user's name from the logged in user's profile.  How do I do that?