Comment 4 for bug 1937354

In order to make progress quickly on this benign issue, I would suggest that you commit the fix as is and close the bug.

The issue of (SETF DOCUMENTATION) accepting NIL while the standard does not mention this specific possiblity, if too controversial, can be fixed into a separate bug. As argued above, this is a useful extension, and it is not prohibited by the standard (see CLHS 1.6 and (SETF DOCUMENTATION) (no explicit restrictions on extensions)).

Thanks.