Broken CSV Output from `convert`

[DavePearce]

Given this trace file:

{"test": { "A": [-1,1] } }

And these constraints:

(module test)
(defcolumns A)
(defpermutation (B) ((+ A)))
(defconstraint test () (vanishes! (+ A B)))

Then we have this:

$ corset convert --format csv --trace permute.trace permute.lisp ; cat trace.csv_test                    
A,B
0x-1,0
0x1,0