The new change_form_submit_buttons template tag had some bad logic in

it that could lead to a failure when adding new objects. It made two bad

assumptions:

change was an object (it's a bool)
It could always compute a delete URL (it can't if change == False).

This change fixes up the logic to treat change correctly and to only

generate a delete URL if we know we're showing the link.

Re-tested all types of pages, including change forms creating a new object.
Unit tests pass.